# Statistics Chapter 1.1-1.2

Define Statistics
The science of collecting, organizing, summarizing, and analyzing information to draw conclusions or answer questions. In addition, statistics is about providing a measure of confidence in any conclusions.

Define Data
A fact or proposition used to draw a conclusion or make a decision.

Descriptive Statistics
Consists of organizing and summarizing information​ collected.

Inferential Statistics
Uses methods that generalize results obtained from a sample to the population and measure the reliability of the results.

Define Population
An entire group to be studied. For example: all students in a university.

Define Individual
A person or object that is a member of a population being studied.

Define Sample
A subset of the population that is being studied.

Define Statistic
A numerical summary of a sample

Define parameter
a numerical summary of a population

Determine whether the given value is a statistics of a parameter: A sample of professors is selected and it is found that 35% own a computer.
Statistic because the value is a numerical measurement describing a characteristic of a sample.

Determine whether the underlined value is a parameter or a statistic. A study of 6,076 adults in public restrooms found that 23 % with underline did not wash their hands before exiting.
The value is a statistic because the 6,076 adults in public rest rooms are a sample
.

What is Qualitative Variable
Allows for classification of individuals based on some attribute or characteristics.

What is Quantitative Variable
Provides numerical measures of individuals. The values of a quantitative value can be added or subtracted and provide meaningful results.

Determine whether the variable is qualitative or quantitative: Grams of carbohydrates in a donut
The variable is quantitative because it is a numerical measure.
.

Determine whether the variable is qualitative or quantitative: Favorite city
The variable is qualitative because it is an attribute
characteristic.

Define Discrete Variable
Quantitative variable that has either a finite number of possible values or a countable number of possible values. You can count them; 0,1,2,3,etc. It usually will say “The number of…”

Define Continuous Variable
Quantitative variable that has either an infinite number of possible values that are not countable.

Determine whether the quantitative variable is discrete or continuous: Population of a city
The variable is discrete because it is countable.

Determine whether the quantitative variable is discrete or continuous: Number of words in a song
The variable is discrete because it is countable.

Determine whether the quantitative variable is discrete or continuous: Depth of a sunken pirate ship
The variable is continuous because it is not countable.

Determine whether the quantitative variable is discrete or continuous: Volume of water in a reservoir
The variable is continuous because it is not countable.

Define observational study
An observational study measures the value of the response variable without attempting to influence the value of either the response or explanatory variables. They can claim association.

Define designed​ experiment
A designed experiment is when a researcher assigns individuals to a certain​ group, intentionally changing the value of an explanatory​ variable, and then recording the value of the response variable for each group. In other words, one group will receive something, and the other will not.

Which allows the researcher to claim causation between an explanatory variable and a response​ variable? An observational study or designed experiment?
A designed experiment.

Determine whether the study depicts an observational study or an experiment.

Fifty patients with brain cancer are divided into two groups. One group receives an experimental drug to fight cancer, the other a placebo. After two years, the spread of the cancer is measured.

The study is an experiment because the researchers control one variable to determine the effect on the response variable.

Determine whether the study depicts an observational study or an experiment.

While shopping, 425 people are asked to perform a taste test in which they eat two randomly placed comma unmarked candies. They are then asked which candy they prefer.

The study is an observational study because the study examines individuals in a​ sample, but does not try to influence the variable of interest.

Determine whether the study depicts an observational study or an experiment.

Fifth-grade students are randomly divided into two groups. One group is taught math using traditional techniques. The other is taught math using a reform method. After 1 year, each group is given an achievement test to compare its proficiency with that of the other group.

The study is an experiment because the researchers control one variable to determine the effect on the response variable.

Define confounding
A study that occurs when the effects of two or more explanatory variables are not separated. Therefore, any relation that may exist between an explanatory variable and the response variable variable may be due to some other variable or variables not accounted for in the study.

For example, a group of old men are divided into two groups; group 1 will breath in smoke and group 2 will not to determine who will get lung cancer. Well they havent accounted for if they were previously smokers.

Define lurking variable
An explanatory variable that was not considered in a study, but that affects the value of the response variable in the study. In addition, lurking variables are typically related to explanatory variables considered in the study.

Define Census
A list of all individuals in a population along with certain characteristics of each individual.