UCLA Stats 13 Quiz Questions Spring 2015 – Flashcards

Select the appropriate word to identify whether the measurement represents a categorical variable or a quantitative variable: The average number of minutes a person watches television each day.

Select the appropriate word to identify whether the measurement represents a categorical variable or a quantitative variable: The name brand of the pair of pants a person is wearing.

Is a person's favorite ice cream flavor (chocolate, vanilla, etc.) a categorical or quantitative variable?

In a large, national study, researchers asked seniors how many alcoholic beverages they had drank in the previous week. The distribution of number of drinks was strongly right-skewed. From this we can conclude that

A set of data is put into numerical order and a statistic is calculated that divides the data set into two equal parts. Which of the following statistics was computed?

A recent housing survey was conducted to determine the price of a typical home in Glendale, CA. Glendale is mostly middle-class, with one very expensive suburb. The mean price of a house was roughly $650,000. Which of the following statements is most likely to be true?

At a hospital they have collected data on the weight (in pounds) and ethnic background (African American, Asian American, Latino, White, and Others) of newborns. What is the best answer?

On the planet Tatooine where the annual famous podrace is held, there is an extensive database of race results going back a couple of decades. Among the variables are the order in which the racers finished (1st, 2nd, 3rd, ...), and their species (Human, Tusken Raider, Ewok, Wookiee, ...). What is the best answer?

Given a categorical variable with sufficient data, should we use a box plot to display our variable?

A random sample of dates taken from headstones at a cemetery in Pleasanton, California, showed an average lifespan of 70 years with a standard deviation of 20 years. Assuming the distribution is unimodal, which of the following is most likely a good description of the distribution? (consider the context in this question)

Suppose that we create a new data set by doubling the highest value in a large data set of positive values. What statement is FALSE about the new data set?

As part of an experiment in perception, 160 UCLA psych students completed a task on identifying similar objects. On average, the students spent 8.25 minutes with standard deviation of 2.4 minutes. However, the minimum time was 2.3 minutes and one students worked for almost 60 minutes. What is the best description of the histogram of times that students spent on this task?

Jim works in the admission office of a major state university in the east coast. He reports that of the 37000 undergraduates who attend this unversity, 47% are male. He then sends an email to every 10th senior and asks them if they plan to go to graduate school and he finds the percentage to be 23%.

Based on past experience, a bank believes that 4% of the people who receive loans will not make payments on time. The bank has recently approved 300 loans. What is the probability that over 6% of these clients will not make timely payments? (You May use the Java Applet to get the answer)

Shelly is going to flip a coin 50 times and record the proportion of heads. Her friend Sidney is going to flip a coin 20 times and record the proportion of heads. Which person is more likely to get 20% or fewer heads?

A set of scores from a vocabulary test given to a large group of international students can be summarized with this five-number summary: {20,35,45,50,60} Determine which of the following statements about the distribution CANNOT be justified.

When a test of significance for the null hypothesis, Ho against the alternative, Ha, the p_value is:

Records at a large university (not UCLA, of course) indicate that 20% of all freshmen are placed on academic probation at the end of the first semester. A random sample of 100 freshmen found that 25% of them were placed on probation. The results of the sample: (Note: You May use the Java Applet to get the answer)

In a large statistics class, the professor has each student toss a coin 12 times and calculate the proportion of his or her tosses that were tails. The students then report their results, and the professor plots a histogram of these several proportions. Should a Normal model be used to represent the sampling distribution of the proportion of tails?

For a class project, every student in a statistics class with 90 students takes a random sample of 200 cars parked at UCLA and records the proportion of clean-air vehicles. (Assume that there are well over 2000 cars parked at UCLA on any given day.) Prior evidence collected by the university suggests that the population proportion is about 10%. Imagine looking at the list of 90 sample proportions. Which of the following is true?

According to the Pew Foundation, in a random sample of 1,044 Americans, only 36% of those sampled thought that global warming is due to human activity (down from 47% last year.) Identify the population, parameter, and statistic.

In Japan there is an annual turkey dog eating contest. The number of turkey dogs that contestants eat are normally distributed with a mean of 36 turkey dogs and a standard deviation of 6 turkey dogs. A contestant eats 27 turkey dogs. What is his z-score?

A histogram of a sample of data shows that the distribution is right-skewed. If the median of the sample is converted to standard units, which of the following is true?

For the overall population, the IQ scores follow the normal distribution with mean equal to 100 and variance equal to 225. What is the best answer?

In standardized scores of achievement motivation that are normally distributed, the US group has a mean score of 35 with a standard deviation of 14. Higher scores correspond to more achievement motivation. Shamu scored in the top 20% of the test takers. What was her score?

Among first-year students at a certain university, scores on the verbal SAT follow the normal curve. The average is around 500 and the standard deviation is about 100. Which of the following statements is correct?

The distribution of the number of hours that college students watch TV per week is unimodal with a mean of 3.7 and a standard deviation of 5. Is it appropriate to use the normal model to approximate the percentage of hours of TV watching within one standard deviation of the mean?

A consulting statistician reported the results from an experiment to the research psychologist, The report stated that on a particular phase of the experiment, a statistical result yielded a p_value = 0.24. Based on this p_value, which of the following conclusions should the psychologist make?

Fluorescent light bulbs have lifetimes that follow a normal distribution, with an average life of 1,685 days and a standard deviation of 1,356 hours. In the production process the manufacturer draws random samples of 197 lightbulbs and determines the mean lifetime of the sample. What is the standard deviation of this sample mean?

A researcher is examining the impact of a new method of teaching Farsi. She concludes that the new method is significantly better than the old method, based on a test with alpha = 0.05.

Which best describes a sampling distribution model of a statistic?

It is believed that 30% of the people in Washington state want cell phone use banned in cafes. The CEO of a major coffehouse chain in Seattle wonders whether the opinion of the people who go to her cafes is different from the overall population. She hires a polling agency to investigate this issue. In a random sample of 1450 individuals, 474 people have the same opinion as the overall population. What is the p-value?

A psychological test was performed on a group of 100 people using lottery tickets. Every participant was given a lottery ticket, and told that the prize was a free trip to the Bahamas. They were also told that one person had the winning ticket, but he or she didn't know that they had it. The participants were allowed to either exchange their ticket for another person's, or they could keep their original ticket. It had been assumed that 50 percent of the population would exchange their ticket for another one, but 72 of the 100 participants chose to do so. What are the null and alternative hypotheses, and which distribution should you use to test these hypotheses?

A researcher is wondering whether a certain medication helps to lower blood pressure. 200 patients with high blood pressure volunteer to participate in the program. They take the medication for six months and record their blood pressure before and after taking the medication. The researcher does the relevant calculations and finds the Z value to be 1.2

The Federalist Papers are a collection of essays written anonymously by some of the Founding Fathers after the American Revolution to try and convince the 13 states to form a federal government. Although we know who the authors are, we aren't sure who wrote which essay. Essay 28 may have been written by Alexander Hamilton or by James Madison. A historian has noticed that in the essays known to be written by Hamilton that are also around 200 sentences long, the average number of sentences started with a preposition are 68. Around 200 sentences were analysed from Essay 28. The historian finds that about 70 sentences start with a preposition, with a standard deviation of 14 sentences. He conducts a test of the hypothesis Ho:μ=68 against Ha:μ≠68. What is his p-value, and what conclusion can he draw from it?

Food inspectors inspect samples of food products to see if they are safe. This can be thought of as a hypothesis test where H0: the food is safe, and HA: the food is not safe. If you are a consumer, which type of error would be the worst one for the inspector to make, a Type I or a Type II error?

The Null and Alternative Hypotheses are statements about values of...

Simulations used to find the distribution we use to find our p-value assume which hypothesis is true?

Suppose you are testing the hypotheses H0=0.5 versus Ha>0.5. You get a sample proportion is 0.54 and find that your p-value is 0.08. Now suppose you redid your study with each of the following changes, will your new p-value be larger or smaller than 0.08 your first obtained? 1) You increase the sample size and still find a sample proportion of 0.54. Your new p-value will be... 2) Keeping the sample size the same, you take a new sample and find a sample proportion of 0.55. Your new p-value will be: 3). With your original sample, you decided to test a two-sided alternative instead of Ha: >0.5. Your new p-value will be:

Suppose you want to determine if a majority of students at your school watched the Super Bowl. You take a random sample of 100 students and find that 54 watched the Super Bowl. You then run an appropriate test of significance. What is the parameter in this situation?

In the Super Bowl scenario from a previous question, suppose that after running the appropriate test you get a standardized statistic of 0.8. What does this standardized statistic mean?

T or F: The Standard of Error(Standard Deviation of the Chance Model) will decrease as the sample size decreases.

The basic premise of hypothesis testing is to assume a status quo statement and examine sample information to assess the validity of the original statement. In order to no longer believe in the validity of the status quo statement, the sample statistic would need to be _______ to the population parameter

Statistical software produces the following output while testing the mean height of a group of children being 45 inches tall. What is the best interpretation of the p-value if it is 0.757?

T or F: The CLT states that the sample distribution model of the sample mean (and proportion) from a random sample is approximately Normal for any n, regardless of the distribution of the population, as long as the observations are independent.

One of the assumptions needed to use a z-distribution for statistical analysis is very difficult to obtain in practice, that is _____

Suppose two researchers wanted to determine if aspirin reduced the chance of a heart attack. Researcher 1 studied the medical records of 500 patients. For each patient, he recorded whether the person took aspirin every day and if the person had ever had a heart attack. Then he reported the percentage of heart attacks for the patients who took aspirin every day and for those who did not take aspirin every day. Researcher 2 also studied 500 people. He randomly assigned half of the patients to take aspirin every day and the other half to take a placebo everyday. After a certain length of time, he reported the percentage of heart attacks for the patients who took aspirin every day and for those who did not take aspirin every day. Suppose that both researchers found that there is a statistically significant difference in the heart attack rates for the aspirin users and the non-aspirin users and that aspirin users had a lower rate of heart attacks. Can both researchers conclude that aspirin caused the reduction?

Scientists are interested in the effects of the sun on growth of moss on trees above the Arctic Circle. 25 years of data is collected and then analyzed. The study shows that the moss grows the most in the years where there is a moderate amount of sun during the summer, and the least in the years where the sun is mostly obscured by clouds during the summer. This is an example of an

A psychologist is examining the effect of showing pictures on learning of words by seven-year-olds. The seven-year-olds are randomly assigned to two groups. The experimental group is shown the word along with the picture. The control group is shown only the word. At the end of the experiment, the subjects are given a test on the number of words they get right. This is an example of:

They are showing a new movie at a neighboring theatre. You are hired to ask a sample of 200 people whether they liked the movie or not. You should compute and report the percentage of the people who said "Yes". What kind of sampling method do you recommend?

A polling agency wants to find out if the proportion of people who vote for candidate X is higher than the proportion who will vote for candidate Y. What statistical method should he use to test this null?

A teacher wants to examine the impact of using technology on teaching microbiology. He teaches two sections of Microbiology; one at eight and one at ten AM on MWF. He randomly assigns one of the classes to teaching with technology. The students in the the technology class get to know that they are part of an experiment and they try really hard to make the class a success. This is an example of

A study indicated that elderly people (age 70 and higher) who had pets lived longer and became less depressed than elderly people who did not have pets. The data came from the records of 700 elderly people who went to a local clinic for treatment. Based on pre-existing medical records, 400 had pets and 300 did not. Choose the best answer.

Several researchers have theorized that humans have longer growth spurts when they live in areas that get more sunlight year-round than other areas. They collect data on the heights of teenaged boys from Equitorial Guinea and from Norway. They also collect data on the hours of sunlight per day for the years that the boys were growing. They conclude that sunlight does cause humans to grow taller.

An examination of the medical records of more than 250,000 women in the 20-40 year age range indicated that those who were overweight had longer than average labor when their first child was born. The study concluded that above average weight causes women in the 20-40 year age range to have longer labor when delivering their first child.

We want to examine the effectiveness of three programs on the weight loss of men and women in the 40-50 year old age range. 150 men and 150 women participate in the study. Subjects are randomly assigned to the three programs. They spend 3-4 hours in the program per week and they continue the program for six months. Their weight is recorded before and after the program. Choose the best answer

Suppose that you wanted to conduct a study and seek the opinion of UCLA undergraduates regarding the elimination of SAT from admission requirements to UCLA. For a large random sample of 600 undergraduate students, the 90% confidence interval is from 0.28 to 0.52. What is the best interpretation of this confidence interval?

A doctor wants to find out if a new medication lowers the blood pressure. 30 patients who have volunteered to take the medication. He measures their blood pressure before taking the medication and six months after taking the medication. What statistical method do you recommend for testing the null hypothesis?

A polling agency wants to find out if the proportion of people who vote for candidate X is higher than the proportion who will vote for candidate Y. What statistical method should he use to test this null?

Armando works in a research institute and they have collected the following data on a random sample of 500 students, Gender GRE score before and after participation in a GRE prep course (GRE is a test you take for entering graduate school) Armando wants to answer questions the following questions: Question one: After taking the GRE preparation course, did women show more improvement on the GRE score or men? Question two: After the GRE preparation course, did more women get admitted to the graduate program or men? What statistical method should he use?

An article in a sociology journal reports a two-tailed p-value of 0.040 for a test of the null hypothesis that there in no difference between the percentage of men and women who endorse marriage outside one's own religion. If the authors had reported a 95% confidence interval in addition to the P value, which of the following would be true?

A researcher wants to compare all students at Kansas State University (population = 22,000) with all residents of the city of Springfield, IL (population = 22,000). He wants to estimate the average age of each population using two separate samples. He wants the same margin of error for each of his sample means. How would the size of the two samples compare?

A consulting statistician reported the results from an experiment to the research psychologist, The report stated that on a particular phase of the experiment, a statistical result yielded a p_value = 0.24. Based on this p_value, which of the following conclusions should the psychologist make?

A researcher wants to find out if the proportion of citizens who endorse spending more money on HIV research is different in states one and two. For a random sample of 200 citizens from state one, 120 endorse spending more money on HIV research. For a random sample of 200 citizens from stat two, 140 endorse spending more money on HIV research. What is the underlying distribution for the above scenario and what is the standard deviation of this distribution?

138 students were taught mathematics through cooperative learning. They were pre-tested and post-tested on their knowledge of fractions and the following data was reported. They wanted to find out if on average the students showed any gain on knowledge of fractions. -Pre-test mean =39.6 -Post-test mean = 59.41 -r (correlation between pre and post data ) = 0.46 -95% CI = 15.8, 23.72

An article in a sociology journal reports a two-tailed p-value of 0.040 for a test of the null hypothesis that there in no difference between the percentage of men and women who endorse marriage outside one's own religion. If the authors had reported a 95% confidence interval in addition to the P value, which of the following would be true?

For the one sample test of the mean If N = 19 For a two tailed test Given that we want 99% confidence, what are the values corresponding to t?

Jordan is testing a hypothesis regarding the effect of having a part time job on the GPA of undergraduate students. For a random sample of 200 undergraduates who have part time jobs and 200 who do not, he finds the following confidence interval for the difference of GPA for students who have part time jobs and those who do not. He finds this confidence interval to be from minus 0.20 to plus 0.20 (-0.20 to +0.20). What is the best answer?

A doctor wants to find out if a new medication lowers the blood pressure. 30 patients who have volunteered to take the medication. He measures their blood pressure before taking the medication and six months after taking the medication. What statistical method do you recommend for testing the null hypothesis?

Jay is testing a null hypothesis regarding the relationship of marital status (married and single) on GPA of graduate students who major in social science. For a random sample of 100 married and 100 single students he finds the following 95% CI for the difference in the GPA of married and single students is from minus 0.40 to plus 0.30 (-0.40 to + 0.30) What is the best answer?

The objective of a study is to find out whether meditation lowers stress level. Thirty six people volunteer to participate in the study. They meditated for one hour and their stress level was measured before and after meditation.

A sociology professor wants to find out if there is a relationship between major and spending junior year abroad. Using the registrar's list she chooses a random sample of 200 non-science majors and 200 science majors and computes the proportion who spend the junior year abroad. What statistical method should this professor use to examine the relationship between major and spending junior year abroad?

A researcher wants to examine the effectiveness of a weight loss program. 100 people volunteer to participate in the study and he randomly assigns 50 of them to the new program which consists of yoga and weight training and 50 to weight training only. He collects the following data weight prior to program weigh after program calories consumed per day gender What is the best analysis to run?

For this research situation, decide what statistical procedure would most likely be used to answer the research question posed. Assume all assumptions have been met for using the procedure. Is ethnicity related to political party affiliation (Republican, Democrat, Other)?

We are interested in seeing is support for a school bond issue differs by neighborhood in a city. What statistical method should we use to answer our question?

A researcher uses a chi-square test to determine if there is a relationship between 2 categorical variables. Which of the following p-values indicates the strongest evidence of such a relationship?

A study claims that there is a relationship between gender (male/female) and the type of magazine (fashion and sport) that people look through when they are on the thread mill. What type of chart would you use to show whether such a relationship exists or not.

A researcher has collected the following information on a random sample of 200 adults in the 40-50 age range: Weight in pounds Heart beats per minute Smoker or non-smoker Single or married He wants to examine the relationship between: 1) heart beat per minute and weight, and 2) smoking and marital status. What is the best answer?

Which of the following is the correct notation for a χ2 -critical value for a sample size of 20 and an α=0.10 for a greater than alternative hypothesis?

Find the value of χ2 (10,0.05)

Which of the following situations will add the largest component to a chi-Square statistic?

In order to test the fairness of a random number generator, a set of 300 numbers is chosen from the set {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}. A tally table for each of the outcomes is prepared. What would the expected value for the occurrence of a seven be?

Forty subjects are asked about their preferred method to obtain the national news daily. They respond in five categories; national newspaper, local newspaper, internet, nightly TV news, or from another individual. How many degrees of freedom does the hypothesis test to determine if there is a statistical difference in preference have?

Forty subjects are asked about their preferred method to obtain the national news daily.They respond in five categories; national newspaper, local newspaper, internet, nightly TV news, or from another individual.If the observed values are all very close to the expected values, the Chi-Square statistic should be ______.