question

Types of epidemiologic studies

answer

Observational and Experimental

question

Examples of Observational studies are

answer

Case control Cohort studies

question

Examples of Experimental studies

answer

Randomized trials

question

What is one objective of epidemiology

answer

To evaluate treatment and prevention measures

question

Randomized trials are also called

answer

Randomized Clinical Trials RCT

question

What type of trial is the best way to evaluate a treatment for benefit and side effects

answer

RCT/ Randomized Trials

question

What are 3 examples of the many applications of RCT/ Randomized Trials (RT)

answer

Drug trials Assess screening programs Deliver health services

question

T or F If there isn't a current treatment to apply to a RT design you cannot move on with the trial

answer

False, can create a treatment vs no treatment group

question

Can you carry out an interventional study without randomizing subjects? Yes or No

answer

Yes

question

What are example studies without comparison groups?

answer

Case study, Case series, Observational study

question

What is one problem with studies without comparisons?

answer

No comparison group means we can't make definite conclusions about cause in relation to treatment and outcome.

question

Name 3 example studies with group comparison

answer

Historical controls, simultaneous non-randomized controls, randomized controls.

question

Please describe Historical controls: (what kind of study is it, how is it conducted...)

answer

Use a current study group for intervention and historic group for control group Compare results of intervention to historic Can be done in cases of fatal diseases - intervention may extend life Can be done when sample size is small

question

What are some problems with using historical controls in experimental studies?

answer

The system of collecting data for the subjects may not be similar to the one used for collecting data on controls, factors other then the interventions being compared can change over time,

question

What is a Simultaneous Non-Randomized Control?

answer

Use a population as a control that has had a different intervention but make it a current population e.g. People admitted to the hospital on odd-numbered days get treatment A (our new intervention), people admitted on even-numbered days get treatment B (the standard treatment) This is non-randomized because there is a pattern to selecting controls IDK

question

What are problems with simultaneous Non-Randomized Controls?

answer

Assignment system may be easy to predict and manipulate Can lead to selection bias when experimenter has an effect on who becomes part of each group

question

Methods of randomization?

answer

Random number table Computer randomization

question

What does stratified randomization guarantee?

answer

Guarantees that randomization is comparable by some variable.

question

List 4 types of data that we want to collect during a study

answer

treatment outcome prognostic profile at entry masking (blinding)

question

Name the two different types of treatment and define

answer

Assigned - assigned Received - assigned one treatment but receives a different one.

question

Why would received treatment differ from assigned treatment

answer

Deliberate Non-compliance Accidental non-compliance

question

T or F

answer

Placebos give good measures of side-effects

question

What is crossover

answer

Time when subjects may switch between study groups: Planned crossover, and Unplanned crossover

question

Planned crossover

answer

Planned crossover Randomly assign subjects to study groups Observe the subjects over time Switch the subjects to the other study group Observe them over time Compare the changes between the subjects with one treatment versus the other treatment

question

Advantages and disadvantages of planned crossover:

answer

Advantages of Planned Crossover Each person in the study is compared to themselves (They act as their own controls) Variables are therefore held constant when comparing treatment outcomes Problems with Planned Crossover You need to be sure that any intervention from the first treatment did not carryover to the second treatment period Washout period The order in which the therapies are given may affect the perceived outcome for the patient

question

What is the washout period?

answer

Washout period is a period of time when the participant is not on any treatment gives time to washout first treatment out of the system

question

Unplanned Crossover

answer

Unplanned crossover May occur if someone in one treatment group needs to be medically managed like the second treatment group instead because of health concerns You may have randomized someone to one treatment group but they decide they don't want to be in that treatment group

question

What is a factorial design ?

answer

Use one study population to study two drugs Drugs must be different and mode of action of each drug (how it works in the body) must be different Allows you to use a study population most economically

question

Describe factorial design 2x2 square

answer

Treatment A on top with + - Treatment B on side with + - Cell a: Both and B Cell b: B only Cell c: A only Cell d: Neither A nor B

question

Name the 3 types of non-compliance

answer

Overt and Covert, accidental non-compliance,

question

What is the effect of non-compliance

answer

to reduce any observed differences in the study groups

question

Type I error and type II error

answer

type 1: alpha treatment differs when they really don't type 2: beta treatments don't differ when they really do

question

1 - Beta

answer

Power = 1 - probability of making a type II error.

question

What are the 5 pieces of information needed to proceed with sample size selection:

answer

Expected difference in the response rate level of alpha that we will be comfortable with power of the study should the study be one sided or two sided

question

T or F: A 2 sided test provides less information but requires more subjects

answer

false

question

Reduction in risk describes what ?

answer

Reduction in risk = efficacy Efficacy = ((rate in those who received old therapy) - (rate in those who received new therapy)/ rate in those ho received old therapy) Describes results of a randomized trial

question

Expressing the results of randomized trials examples for describing the results of a randomized trial

answer

Differences in survival curves of two groups NNT number of patients who would need to be treated: 1/ (rate in untreated group) - (rate in treated group) NNH: number needed to harm

question

Drug discovery process

answer

is very long: target discovery --> target validation --> assay development --> screening and hits to leads --> lead optimization --> development --> clinical trials --> market.

question

What are the 4 phases of clinical drug trials?

answer

Phase I - small studies that look at potential toxic effects and pharmacologic effects of new drugs Phase II - A larger study to determine how effective the drug is and how safe it is Phase III - Large-scale trial of the drug for effectiveness and safety (limited time) Phase IV - Long-term surveillance of safety of a drug

question

Cohort studies are used to....

answer

Link an exposure to a disease

question

In a basic cohort study we are looking for... (prevalence or incidence) ?

answer

Looking for incidence, new cases of disease developing over time, compare that in two groups. Air plane mechanics

question

Incidence Rate in Exposed

answer

(Exposed and develop disease ) / ( Exposed and develop disease + exposed and don't develop disease)

question

Incidence Rate in Not-Exposed

answer

(Not Exposed and develop disease) / (Not Exposed and develop disease + not exposed and don't develop disease)

question

T or F: A cohort study includes randomization of study subjects into the two study groups.

answer

False: Comparing Cohort and Randomized: Both studies compare exposed and non-exposed groups In a randomized trial it may be treatment In a cohort study it may be a factor that caused disease A cohort study does not include randomization of study subjects into the two study groups By design, you need people who were exposed in one group and unexposed people in the other Without randomization we are left with a question of whether association is causal You can randomly sample from the population of exposed and unexposed people to obtain your study groups

question

T F Randomization trials are the gold standard

answer

True

question

What are the advantages of a Cohort study?

answer

Advantages of Cohort studies You get information on the sequence of events (exposure followed by outcome) which helps to establish causality You can follow many outcomes with one group Recall bias is minimized You can measure the exposure

question

What are disadvantages of a cohort study?

answer

Usually they involve a large study group over a long period of time so they are expensive and time-consuming May not be a good study design for diseases with long latency periods If it takes too long for the disease to develop you may lose participants or not be able to carry out the study for that long Not a good design for rare diseases; you would need an extremely large study population Withdrawals Exposures may change during the study period

question

Cohort measures what?

answer

Disease Incidence

question

What is prospective cohort study also called?

answer

Concurrent Cohort Longitudinal study

question

What are prospective cohort study?

answer

This is the design where subjects are identified at or before the exposure and followed over time to measure outcomes May be limited by money, lifespan of investigator, participation of subjects Gives good information on potential causative association between exposure and disease

question

What is retrospective cohort study also called?

answer

Historical cohort study or non-concurrent prospective study

question

What is a retrospective cohort study?

answer

In this design, subjects have had the exposure in the past and you obtain this information from records You then look for the outcome of interest when you begin the study

question

In the Nurses Health Study Questionnaire of 1974 to 1976, 14,000 married women reported male vasectomy as the couple's form of birth control Study population was contacted in 1989 to determine incidence of prostate cancer in men with vasectomies Concluded that vasectomy did increase risk of prostate cancer. This is an example of what king of study...

answer

Retrospective Cohort Study

question

What are the strengths and limitations of prospective cohort study ....

answer

Strengths more reliable exposure data data available for potential confounding factors Limitations longer completion time more expensive

question

What are the strengths and limitations of historical cohort study....

answer

Strengths shorter completion time less expensive Limitations less reliable exposure data data on potential confounding factors may be missing

question

Explain the Framingham Heart Study

answer

Began in 1948 as a response to increasing rates of Cardiovascular Disease (CVD) Goal was to study common lifestyle patterns related to risk of cardiovascular disease At the time, risk factors for CVD such as smoking, diet, exercise habits, etc, were unknown The study included 50,209 men and women from the town of Framingham, Massachusetts Initial study participants were between the ages of 30 and 62 Participants answer questionnaires and have clinical measurements taken every two years The study is still ongoing A second generation was enrolled in 1971...these were adult children of original participants and their spouses In 2003 a third generation was enrolled...grandchildren of original participants

question

The Framingham Heart Study: Research Milestones:

answer

Research Milestones 1960 - Cigarette smoking found to increase the risk of heart disease 1970 - High blood pressure found to increase the risk of stroke 1988 - High levels of HDL cholesterol found to reduce risk of death 2002 - Obesity is a risk factor for heart failure 2008 - Based on analysis of a social network of 12,067 people participating in the Framingham Heart Study (FHS), researchers discover that social networks exert key influences on decision to quit smoking 2009 - A new genetic variant associated with increased susceptibility for atrial fibrillation, a prominent risk factor for stroke and heart failure, is reported in two studies based on data from the Framingham Heart Study

question

Difficulty in the Framingham Heart Study:

answer

Diversity differences between the population of Framingham and the rest of the US An Omni cohort was added to the study in 1994 to address the need for more racial and ethnic diversity in the study An unrelated second Omni generation was studied from 2003 to 2005 Difficulties in recruitment of original study cohort Study designers hoped to obtain all participants by random sampling but had to ask for volunteers for a large enough sample size

question

Describe the National Children's Study

answer

Long-term longitudinal study in the US to look at environmental and genetic influences on children's health Follow 100,000 children from before birth to age 21 Look at environmental factors like water, air, nutrition, care, and others Make associations about outcomes such as asthma, obesity, mental health disorders, injuries, and others 105 Study locations throughout the United States In Florida... Study Centers were chosen by a method that would ensure representation of varied "ethnic, racial, economic, religious, geographic, and social groups" This will help make the study generalizable to the population of the US

question

Anything else about the National Children's Study:

answer

Study enrollment began in 2009 in seven study locations Thirty more study centers will enroll participants in late 2010 "Vanguard" study locations are set up to test recruitment methods Provider-based Recruitment Enhanced Household-based Recruitment High Intensity/Low Intensity Dynamic Model

question

Anything Else about the National Children's Study:

answer

Participants answer questionnaires and phone calls, have height and weight measurements taken, have blood, urine, and hair samples collected, and other measurements Investigators may take dust and water samples from the home

question

Challenges with the National Children's Study:

answer

Controversy over the proposed cost of the study and how much funding will be provided Difficulty in household-based recruitment Difficulty in recruiting in some rural areas (perception concerns) Language challenges Ethical challenges

question

The Dutch Famine Birth Cohort Study:

answer

Retrospective cohort study to examine the association between under nutrition during pregnancy and Cardiovascular disease in the offspring During the winter of 1944 and 1945 in the Northern Netherlands, food transports were blocked by Nazi troops Adult rations ranged from 400 to 800 calories per day "The Hungerwinter" The study began in 1994 Records were examined for babies born between Nov. 1, 1943 and Feb. 28, 1947 in a hospital in Amsterdam These people were located and 900 agreed to participate in the study at age 50 850 of these again participated at age 59

question

What were the study findings for the Dutch Famine Birth Cohort Study?

answer

People conceived during the famine have 3 times the risk of coronary hearty disease prevalence as those not conceived during famine People malnourished in utero had higher rates of type II diabetes There was no association between those conceived during the famine and elevated blood pressure

question

T or R: The Dutch Famine Birth Study would be unethical to carry out as a prospective study so a retrospective study was necessary?

answer

True

question

What were advantages and disadvantages of the Dutch Famine Birth Cohort Study?

answer

Advantages Record-keeping is very good in Holland, which allowed study subjects to be identified and contacted Records on the level of famine during different gestational periods were available Disadvantages The study population may not be reflective of the general population at the time because of high infant mortality during the Hungerwinter

question

What were some example bias in assessment of the outcome for the Dutch Study?

answer

The person who measures the outcome may know who has been exposed and who hasn't and this knowledge may affect their assessment of who has the outcome of interest May need to mask (blind) the person who measures the outcome

question

Information Bias?

answer

If the information on the exposed group is more complete than the information on the non-exposed group (or vice-versa) then bias may be introduced This could especially be a problem with retrospective cohorts Need to ensure that the records are equally good for both the exposed group and non-exposed group

question

How might biases from non-response and losses to follow up affect outcome measures?

answer

This may affect outcome measures and make a study difficult to interpret

question

What is analytic bias?

answer

Anyone involved in data analysis may have their own bias that the can introduce which may affect the study interpretation

question

T or F a prospective cohort study works well if the time between exposure and outcome is relatively long.

answer

F. Want it short to minimize loss to follow-up

question

What is the design method of a case-control study?

answer

people with an illness are compared to those without an illness This comparison allows you to relate an exposure to an illness

question

What are cases

answer

Cases are people who have disease

question

What are controls

answer

Controls are people who don't have disease

question

In a case-control study how do you determine the exposure that is associated with a disease?

answer

To determine the exposure that is associated with a disease, we look at the proportion of cases exposed and the proportion of cases not exposed We also look at the proportion of controls exposed and the proportion of controls not exposed

question

What are measuring in a case-control study?

answer

In a case-control study you are measuring a past exposure that lead to disease

question

How do you set up the 2x2 table for a case-control study

answer

cases and controls on top exposed and not exposed on side a b c d total = a+c b+d proportion exposed: a/a+c and b/b+d

question

T or F: If there is an association of the exposure with the disease then I would expect a higher proportion of the controls to have been exposed than the cases.

answer

False it's cases vs controls not controls vs cases ...

question

Study break. Good job.!

answer

:D So a woman got arrested for battery. Guess what she did? She threw cupcakes. lol, well by law, throwing stuff at people is battery no matter how cute the things we throw are (pillows, ice cream, cupcakes....). Would this uphold in court, most likely not.

question

54 women with breast cancer and 150 women without breast cancer of the women with breast cancer 35 have a history of 1 or more alcoholic drinks a day of those w/out 61 have a history of 1 or more alcoholic drinks per day. Set up your table.

answer

cases controls alcohol + 35 61 alcohol - 54 150

question

What are two comparisons between a cohort and a case-control study?

answer

Both are observational studies Both give information about the association between an exposure and a health outcome Both case-control and cohort studies may be stratified by exposure

question

What are some differences between a cohort study and a case-control study?

answer

A cohort study starts with the exposure of interest and measures disease outcome We are comparing people with exposure to people without exposure A case-control study starts with disease outcome and looks for exposure We are comparing people with disease to people without disease

question

In a study of the association between alcohol and breast cancer how would you set up a cohort? case-control?

answer

Cohort study - start with people who drink or don't drink and follow for development of breast cancer over time; analyze your outcome in terms of number of drinks per day Case-control study - start with people with or without breast cancer and interview them about drinking habits; analyze your cases and controls in terms of number of drinks per day

question

Where can you select cases? What kind of cases can you use and what are their respective advantages?

answer

Hospital or clinic Disease registries Incident Cases The advantage of using incident cases is that you gain information on risk related to development of disease, not disease survival Prevalent Cases The advantage of using prevalent cases is that you don't have a larger pool of participants

question

Where can you select controls?

answer

Non-hospitalized people Door-to-door recruiting This involves identifying a case and then selecting a control in the same neighborhood Requires a lot of time, may be safety issues Telephone recruiting Random-digit dialing using the first three numbers of the exchange to stay within a geographic area and randomizing the last four numbers Faster than door-to-door, safer Drawbacks in developed countries many people no longer have landlines, only cell phones In developing countries many people don't have phones School enrollment lists Insurance company lists Selective service registry Referral from a friend/family member who is a case in the study Hospitalized people Easier to identify and "recruit" or gather data on Not an ideal control group May not represent the population with regard to risk factors/exposures May not even be similar to other hospitalized patients Use a sample of all patients or use a specific diagnosis for controls?

question

T or F: when identifying cases to enroll in a case control study, case should be historic and incidence cases.

answer

True

question

What does matching cases and controls help with?

answer

Matching controls to cases helps to ensure similarity in the two groups

question

Name two types of matching.

answer

Group matching aka frequency matching This is matching characteristics of cases and controls by proportions Usually would select all cases first, determine proportions for matching, and select controls to match the proportions Individual matching aka matched pairs Individually match each control to a case

question

Of my cases, 30% are of Hispanic descent, so I'll choose controls so that 30% of that group are of Hispanic descent What kind of matching is this?

answer

Group!

question

I've enrolled a 50-year old female as a case, so I'll look for a 50-year old female as a control What kind of matching is this?

answer

Individual matching!

question

What is the end result of individual matching?

answer

Matched case-control pairs.

question

What are two types of problems with matching (category names and then describe)?

answer

Practical problems Trying to match by too many characteristics makes it difficult to find controls Conceptual problems If you match by a characteristic, then you can't study that characteristic e.g., If I'm studying the association between socioeconomic status and depression, and I match by annual income; there will be no SES differences in my groups

question

Problems of recall?

answer

Limitations in recall People may not remember the information you're looking for, or they may not know the information you're looking for Recall bias Some people may have better memories of certain events than others

question

T or F: statistically it is best to use more than one control per case? (Multiple controls of the same type)

answer

True

question

Law of diminishing returns ....states

answer

there is little benefit in having more than 4 controls per case

question

What compare cases to one control group, but include a second control group as another comparison?

answer

Multiple Controls of Different Types

question

A case-control study of whether mothers of children with brain tumors were exposed to more prenatal radiation than control mothers. What are the cases, what are the controls?

answer

Cases were children with brain tumors Controls were... Children with no cancer Children with cancer other than brain tumors

question

T or F: You can gain the advantages of both cohort and case-control studies by using a hybrid of the two. What is it called if true?

answer

True. Defined cohort

question

Nested case-control studies Case-Cohort studies are examples of what?

answer

hybrid case-control-Cohort studies

question

Describe nested case-control

answer

When a case is identified (develops disease) a control who is at risk for the disease but does not have the disease is identified from the cohort (matched) This approach reduces the potential recall bias of a case-control study and is faster and less expensive than a full cohort study Controls may turn into cases during the study period (Choose more than one control per case)

question

Describe case-cohort studies

answer

Cases develop over time, and controls are randomly selected from the cohort at the end of the study Cases and controls are not individually matched

question

What are the advantages of embedding a case-control study in a defined cohort?

answer

Limits recall bias Allows collection of biological data long before clinical disease develops (identify risk factors more accurately?) Less expense...you collect all specimens but only conduct lab work on those who become part of the study All cases and control come from the same cohort so they are likely to be comparable

question

What are two other study designs?

answer

Case-Crossover design Cross-Sectional design (observational study designs )????

question

Describe Case-Crossover Design:

answer

Used for exposures that are short in duration and occurrence Used for acute outcomes Good for studying acute illness potentially associated with environmental exposures e.g., Myocardial infarction and air pollution May be subject to recall bias if you are not using a scientific measurement

question

Describe Cross-Sectional Study:

answer

Exposure and disease outcome are identified simultaneously for a study subject Snapshot of the population Cases are prevalent cases of disease (also called a prevalence study) Often these studies are done by questionnaires e.g., study of physical fitness and Type II diabetes might assess fitness level and disease status at one point

question

For Cross-sectional is it a temporal relationship or "here and now"

answer

here and now? idk

question

What are some problems with cross-sectionals studies?

answer

We are dealing with prevalent cases only, which won't include people who have died Is there an association of the exposure with the development of disease or survival with the disease? May not be able to establish a temporal relationship between the exposure and the disease

question

Study Designs: Randomized Clinical trial

answer

Study Population --> randomly assigned --> Current Treatment and New Treatment --> Improve Do Not Improve x2

question

Study Designs: Exposed Not Exposed --> Have the Disease, Exposed Not Exposed --> Do Not Have The Disease

answer

Case Control

question

What is absolute risk?

answer

The risk of developing a disease is the probability that event happening Absolute Risk This is the incidence of disease in a population Also defined as the probability of an event occurring in a study population Incidence = (# of new cases)/ ( # of people at risk)

question

T or F: Absolute risk is useful for association

answer

F

question

What are 2 potential ways to know whether there is an excess risk of disease in an exposed group versus an unexposed group

answer

Ratio This is the ratio of the risk (or incidence of disease) of each group developing disease Disease risk in exposed/Disease risk in unexposed Difference (Also called Attributable risk) This is the absolute difference in the two numbers (Disease risk in exposed) - (Disease risk in unexposed)

question

Attributable Risk and Relative Risk

answer

Attributable risk (Difference) Tells you how much additional incidence of disease is due to exposure Chapter 12 Relative Risk (Ratio) Tells you how many times more likely an exposed person is to get a disease than a non-exposed person RR = Risk in exposed/risk in unexposed = incidence in exposed/incidence in unexposed The relative risk tells us the probability of disease in an exposed group compared to the probability of disease in an unexposed group

question

Relative risk:

answer

Why do we do cohort or case-control studies? we are looking for an association between and exposure or risk factor and a disease We want to know what is the risk of developing disease from an exposure compared to the risk of developing disease without an exposure We want to quantify the association so we can determine how strong it is Relative risk will give us a number that is the ratio of the risk in the exposed group over the risk in the unexposed group What does this number mean?

question

If RR is X= 1 , X >1 , X or <1

answer

If a RR is equal to 1: Then the numerator and the denominator are equal and there is no difference in the incidence in exposed and unexposed groups Exposed people are not at greater risk of disease There is no evidence of any association between exposure and disease If an RR is greater than 1: Then the numerator is higher than the denominator and there is a difference in the incidence in exposed and unexposed groups Exposed people are at greater risk of disease There is a positive association between an exposure and a disease (it may be causal) If an RR is less than 1: Then the numerator is lower than the denominator and there is a difference in the incidence in exposed and unexposed groups Exposed people are at lower risk of disease There is a negative association between an exposure and a disease (The exposure may be protective)

question

T or F: Cohort studies always use disease incidence

answer

True Incidence in exposed = a/a+b Incidence in nonexposed = c/c+d RR = incidence exposed/ incidence non exposed = (a/a+b)/ ( c/c+d)

question

In a cohort study of the association between sports concussions and early onset of dementia, a total of 4142 football players were enrolled. Of these, 2140 had the exposure of interest and 428 of the exposed developed early onset of dementia. Of the unexposed players, 196 developed early onset of dementia. The Relative Risk of the association between sports concussions and early onset of dementia is:

answer

This = 2.04 :D

question

Can we use RR in a case control study

answer

NO May be incident or prevalent cases enrolled Once they are part of the study, they are all cases and we don't have an incidence rate for that study group (no measure of risk) So we can't use a Relative Risk in a Case Control Study we use ODDS ratio

question

T or F: odds ratio may be used in a cohort study

answer

True

question

Odds Ratio (Relative Odds)

answer

(Odds than an exposed person develops disease/odds that a non-exposed person develops disease ) = (a/b)/(c/d) = (ad)/(bc) This is the ratio of the odds of developing a disease in an exposed population to the odds of developing a disease in a non-exposed population AKA Relative Odds

question

How is OR interpreted?

answer

If a OR is equal to 1: There is no evidence of an association between exposure and disease If an OR is greater than 1: There is a positive association between an exposure and a disease (it may be causal) If an RR is less than 1: There is a negative association between an exposure and a disease (The exposure may be protective)

question

Differences between RR and OR

answer

The Relative Risk is the ratio of the probability of an event occurring in the exposed group versus the unexposed group If a study of smoking and heart disease has a RR of 3.0 then a smoker is 3 times more likely to develop CHD than a non-smoker The Odds Ratio is the probability that an event will occur divided by the probability that it won't occur If a study of smoking and heart disease has an OR of 3.0 then the odds of being a smoker and developing CHD is 3 times the odds of not being a smoker and developing CHD

question

OR or RR: If a study of smoking and heart disease has a ___ of 3.0 then a smoker is 3 times more likely to develop CHD than a non-smoker

answer

RR

question

OR or RR: If a study of smoking and heart disease has an ___of 3.0 then the odds of being a smoker and developing CHD is 3 times the odds of not being a smoker and developing CHD

answer

OR

question

T or F: OR is the only outcome measure for a case control study

answer

True

question

Which is the preferred measurement in Epi OR or RR

answer

RR

question

T or F: Can estimate the RR based on the odds ratios that were calculated

answer

T

question

When is the OR a Good Estimate of RR?

answer

An OR is a good estimate of RR when: The cases in the study have the same history of exposure as the whole population with disease from which those cases were drawn This should be true if we randomly sampled for cases The controls in the study have the same history of exposure as the whole population without disease from which those controls were drawn This should be true if we randomly sampled for controls The disease is rare This you can determine

question

Know this article: Schulman et al: The Effect of Race and Sex on Physicians' Recommendations for Cardiac Catheterization. N Eng J Med 1999; 340: 619-625

answer

EXAMPLE OF HOW FAILURE TO UNDERSTAND WHAT AN ODDS RATIO MEANS CAN LEAD TO TROUBLE

question

T or F: Matching affects the way you calculate OR for the study

answer

T

question

What is OR for : A) 6, B) 4 c) 3 d) 7

answer

cross: 6*7/4*3 = 42/12 = 3.5

question

Concordant pairs and Discordant pairs (Matched Pair Case Control Study)

answer

Dis: 3. Pairs in which the case was exposed but the control was not 4. Pairs in which the control was exposed but the case was not con: Pairs in which both the case and the control were exposed Pairs in which neither the case nor the control were exposed Concordant pairs are matched pairs that had the same exposure experience Discordant pairs are matched pairs that had different exposure experiences

question

More about Matched Piar case study

answer

The concordant pairs tell us nothing about association case and control had same exposures The OR for matched pairs is the ratio of the discordant pairs OR (matched pairs)= (pairs in which case was exposed but control was not/ pairs in which control was exposed but case was not) OR (matched pairs) = b/c

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