Stats chap 4/Unit 3 Questions

As part of a demographic study, a college administrator needed to survey a sample of students from the college. From each major offered at the college, the administrator randomly selected 5 percent of the students with that major to participate in the survey. Which of the following is the best description of the type of sample selected by the administrator? And why?

A) cluster sample
B) convenience sample
C) simple random sample
D) stratified random sample
E) systematic random sample

To investigate whether the consumption of beetroot juice enhances exercise performance, a researcher selected a random sample of 50 student athletes from Al, the students athletes at a college. The athletes in the sample were randomly assigned to one of two groups. In one group, 25 athletes were given a daily dose of beetroot juice, and in the other group, the remaining athletes were given a daily dose of placebo. At the end of the six weeks of exercise training, the researcher compared the performances of two groups. Based on the design of the investigation, which of the following is the largest population to which results can be generalized?

A) the 25 student athletes assigned to the beetroot juice group
B) the 50 student athletes in the sample
C) all student athletes at the college
D) all students at the college
E) all people who exercise

To compare the effectiveness of two treatments, researchers conducted a well designed experiment using a randomized block design in which the subjects were blocked by age group (under 40 years and 40 years or older). Which of the following must be true about the randomized block design of the experiment?

A) the number of subjects in each block is different
B) treatments are randomly assigned to subjects within each block
C) the design cannot have a control group because subjects are blocked by age group
D) The experiment uses a matched pairs design, where subjects from one block are paired with subjects from the other block
E) the subjects in one block receive one treatment and the subjects in the other block receives the other treatment

A simple random sample of size n is one in which

A) every nth member from the population is selected
B) you keep sampling until you have a fixed number of people having various characteristics
C) there is exactly the same proportion of women in the sample as in the populations
D) each possible sample size n have the same chance of being selected

A new headache remedy was given to a group of 25 subjects who had headaches. Four hours after taking the new remedy, 20 of the subjects reported that their headaches had disappeared. From this information you conclude

a) that the remedy is effective for the treatment of headaches.
b) nothing, because there is no control group for comparison.
C) nothing, because the sample size is too small.
d) that the new treatment is better than aspirin.
e) that the remedy is not effective for the treatment of headaches.

Researchers used two footballs of the same size to examine the effect of helium on kicking distance. One football was filled with air, and the other was filled with helium. Eleven people participated in the study. Each person kicked the football filled with air and the football filled with helium, and the kicking distances, in yards, were recorded. The football that was kicked first was determined by the flip of a fair coin, and the people did not know which football was filled with air and which was filled with helium. What type of study was conducted by the researchers?

a) A completely randomized design
b) A matched-pairs design
C) An observational study
d) A sample survey
e) A census

A program exists to encourage more middle school students to major in math and science when they go to college. The organizers of the program want to estimate the proportion of students who, after completing the program, go on to major in math or science in college. The organizers will select a sample of students from a list of all students who completed the program. Which of the following sampling methods describes a stratified random sample?

a) Select all female students on the list.
b) Randomly select 50 students on the list.
C) Randomize the names on the list and then select every tenth student on the randomized list.
d) Randomly select 25 names from the female students on the list and randomly select 25 names from the male students on the list.
e) Randomly select 50 students on the list who are attending college.

Some researchers believe that too much iron in the blood can raise the level of cholesterol. The iron level in the blood can be lowered by making periodic blood donations. A study is performed by randomly assigning half of the group of volunteers to give periodic blood donations while the rest do not. What kind of study is this?

a) An experiment with a single factor.
b) An experiment with a control group and blinding
C) An experiment with blocking
d) An observational study with comparison and randomization.
e) An observational study with little if any bias.

In a test of roughly 200 men and women, those with moderately high blood pressure did worse on tests of memory and reaction time than those with normal blood pressure. This is an example of a

a) simple random sample
b) controlled experiment
c) observational study
d) cluster experiment
e) report

Control groups are used in experiments in order to

a) achieve a proper and uniform level of randomization.
b) control the subjects of a study to ensure that all participate equally.
C) guarantee that someone other than the investigators, who have a vested interest in the outcome, controls how the experiment is conducted.
d) as a benchmark to compare to responses to actual treatments.
e) reduce the variability in results.

As part of a study on facility needs, the administrators of a university wanted to estimate the percent of students who use the exercise facilities on a regular basis. From the 34,000 students who attend the university, a random sample of 370 male students and 400 female students was selected. Of the 770 students selected, 493 students indicated that they use the exercise facilities on a regular basis. What are the population and the sample of the study?

a) The population is the 770 students who were selected, and the sample is the 493 students who indicated
that they use the exercise facilities on a regular basis.
b) The population is the 770 students who were selected, and the sample is whether each student in the
survey uses the exercise facility on a regular basis.
C) The population is the 34,000 students who attend the university, and the sample is whether each student in
the survey is male or female.
d) The population is the 34,000 students who attend the university, and the sample is the 770 students who were selected.
e) The population is the 34,000 students who attend the university, and the sample is the 493 students who
indicated that they use the exercise facilities on a regular basis.

A survey is to be administered to recent graduates of a certain nursing school in order to compare the starting salaries of women and men. For a random sample of graduates, three variables are to be recorded: sex, starting salary, and area of specialization. Which of the follow best describes a conclusion that can be drawn from this study?

a) Whether being female causes graduates of this nursing school to have lower (or higher) starting
salaries than males.
b) Whether being female causes graduates in this sample to have lower (or higher) starting salaries than males.
C) Whether choosing certain area of specialization causes females graduates of this nursing school to have lower (or higher) starting salaries than males.
d) Whether there is an association between sex and starting salary among graduates of this nursing school.
e) Whether there is an association between sex and starting salary at all nursing schools similar to this one.

Will storing batteries in a freezer make them last longer? To find out, a company that produces batteries takes a random sample of 100 AA batteries from its warehouse. The company statistician randomly assigns 50 batteries to be stored in a freezer and the other 50 to be stored at room temperature for 3 years. At the end of that time period, the batteries stored in the freezer had a higher charge, and the difference was statistically significant. What conclusion can we draw from this study?

a) Nothing, since this was not a controlled experiment.
b) We can infer cause and effect, because the batteries were randomly assigned to one of two
treatments.
C) We can infer that the result holds for the population of batteries produced by this company
because the batteries were randomly chosen to be in the experiment.
d) Both b and c.
e) Nothing, because the research was not performed by someone outside of the company.

Three brands of popcorn are to be tested in an experiment to determine the best brand for percent of kernels popped. Two hundred kernels of each are to be placed in three air poppers and heated until there are no more pops. The unpopped kernels are then counted and compared. How might the investigator control for the differences due to the three air poppers? ludis,

a) Use a random number generator to match the brand of popcorn to one of the poppers
b) Run three iterations of the experiment with 200 kernels of each brand popped in each popper and count the number of unpopped from the three trials.
C) Randomly mix the three brands and divide the mix evenly into each popper.
d) Increase the number of kernels to increase the sample size and thereby reduce variation.
e) Form clusters of kernels which mirror the population of kernels.

Recently, a group of adults who swim regularly for exercise were evaluated for depression. It turned out that these swimmers were less likely to be depressed than the general population. The researchers said the difference was statistically significant.

1. What does statistically significant mean in this

Recently, a group of adults who swim regularly for exercise were evaluated for depression. It turned out that these swimmers were less likely to be depressed than the general population. The researchers said the difference was statistically significant.

2. Is this an experiment or an observational study? Explain.

Recently, a group of adults who swim regularly for exercise were evaluated for depression. It turned out that these swimmers were less likely to be depressed than the general population. The researchers said the difference was statistically significant.

News reports claimed this study proved that swimming can prevent depression. Explain why

An automobile manufacturer sold 30,000 new cars, one to each of 30,000 customers, in a certain year. The manufacturer was interested in investigating the proportion of the new cars that experienced a mechanical problem within the first 5,000 miles driven.

A list of the names and addresses of all customers who bought the new cars is available. Describe a
sampling plan that could be used to obtain a simple random sample of 1,000 customers from the list.

An automobile manufacturer sold 30,000 new cars, one to each of 30,000 customers, in a certain year. The manufacturer was interested in investigating the proportion of the new cars that experienced a mechanical problem within the first 5,000 miles driven.

Each customer from a simple random sample of 1,000 customers who bought one of the new cars was asked
whether they experienced any mechanical problems within the first 5,000 miles driven. Forty customers from the sample reported a problem. Of the 40 customers who reported a problem, 13 customers reported a problem specifically with the power door locks. Based on this sample, what would be a good estimate of the number of customers who purchased a new car this year and had problems with the power door locks?

The state of Louisiana has been receiving a lot of complaints from families of residents of nursing homes owned by a certain company. This company owns 12 nursing homes throughout the state, and each home serves 30 residents and offers three levels of care: Limited Assistance, Full Assistance, and Premium assistance. The state wants to conduct a sample survey of residents of these nursing homes to determine if the quality of care meets minimum standards.

Describe a cluster sample and a stratified sample which will sample about 60 residents.

The state of Louisiana has been receiving a lot of complaints from families of residents of nursing homes owned by a certain company. This company owns 12 nursing homes throughout the state, and each home serves 30 residents and offers three levels of care: Limited Assistance, Full Assistance, and Premium assistance. The state wants to conduct a sample survey of residents of these nursing homes to determine if the quality of care meets minimum standards.

Which sample do you think will provide the state with the most accurate information? Why?

A political scientist at UNO conducted a phone interview survey which aimed to study the effect of
race of the interviewer. Following the interview, the respondents were asked whether they thought the interviewer was black or white (all the interviewers were black). One of the questions asked was "Do you agree with the following statement: The Black Lives Matter coalition is the newest chapter of the Civil Rights Movement.". Of the respondents who thought the interviewer was black, 43% agreed with the statement. Of respondents who perceived a white interviewer, 19% agreed with the statement. Which type of bias does this illustrate? Why?