1. A randomized experiment was done by randomly assigning each participant either to walk for half an hour three times a week or to sit quietly reading a book for half an hour three times a week. At the end of a year the change in participants' blood pressure over the year was measured, and the change was compared for the two groups.
If a statistically significant difference in blood pressure change at the end of a year for the two activities was found, then:
a. It cannot be concluded that the difference in activity caused a difference in the change in blood pressure because in the course of a year there are lots of possible confounding variables.
b. Whether or not the difference was caused by the difference in activity depends on what else the participants did during the year.
c. It cannot be concluded that the difference in activity caused a difference in the change in blood pressure because it might be the opposite, that people with high blood pressure were more likely to read a book than to walk.
d. It can be concluded that the difference in activity caused a difference in the change in blood pressure because of the way the study was done.
2. What is one of the distinctions between a population parameter and a sample statistic?
a. A population parameter is only based on conceptual measurements, but a sample statistic is based on a combination of real and conceptual measurements.
b. A sample statistic changes each time you try to measure it, but a population parameter remains fixed.
c. A population parameter changes each time you try to measure it, but a sample statistic remains fixed across samples.
d. The true value of a sample statistic can never be known but the true value of a population parameter can be known.
3. A magazine printed a survey in its monthly issue and asked readers to fill it out and send it in. Over 1000 readers did so. This type of sample is called
a. a cluster sample.
b. a self-selected sample.
c. a stratified sample.
d. a simple random sample.
4. Which of the following would be most likely to produce selection bias in a survey?
a. Using questions with biased wording.
b. Only receiving responses from half of the people in the sample.
c. Conducting interviews by telephone instead of in person.
d. Using a random sample of students at a university to estimate the proportion of people
who think the legal drinking age should be lowered.
5. Which one of the following variables is not categorical?
a. Age of a person.
b. Gender of a person: male or female.
c. Choice on a test item: true or false.
d. Marital status of a person (single, married, divorced, other)
6. A polling agency conducted a survey of 100 doctors on the question “Are you willing to treat
women patients with the recently approved pill ABX-123”? The conservative margin of error
associated with the 95% confidence interval for the percent who say 'yes' is
a. 50%
b. 10%
c. 5%
d. 2%
7. Which one of these statistics is unaffected by outliers?
a. Mean
b. Interquartile range
c. Standard deviation
d. Range
8. Which of the following would indicate that a dataset is not bell-shaped?a. The range is equal to 5 standard deviations.
b. The range is larger than the interquartile range.
c. The mean is much smaller than the median.
d. There are no outliers.
9. The value of a correlation is reported by a researcher to be r = −0.5. Which of the following
statements is correct?
a. The x-variable explains 25% of the variability in the y-variable.
b. The x-variable explains −25% of the variability in the y-variable.
c. The x-variable explains 50% of the variability in the y-variable.
d. The x-variable explains −50% of the variability in the y-variable.
10. What is the effect of an outlier on the value of a correlation coefficient?
a. An outlier will always decrease a correlation coefficient.
b. An outlier will always increase a correlation coefficient.
c. An outlier might either decrease or increase a correlation coefficient, depending on
where it is in relation to the other points.
d. An outlier will have no effect on a correlation coefficient.
11. One use of a regression line is
a. to determine if any x-values are outliers.
b. to determine if any y-values are outliers.
c. to determine if a change in x causes a change in y.
d. to estimate the change in y for a one-unit change in x.
12. A chi-square test of the relationship between personal perception of emotional health and marital status led to rejection of the null hypothesis, indicating that there is a relationship between these two variables. One conclusion that can be drawn is:
a. Marriage leads to better emotional health.
b. Better emotional health leads to marriage.
c. The more emotionally healthy someone is, the more likely they are to be married.
d. There are likely to be confounding variables related to both emotional health and marital status.
13. A chi-square test involves a set of counts called “expected counts.” What are the expected
counts?
a. Hypothetical counts that would occur of the alternative hypothesis were true.
b. Hypothetical counts that would occur if the null hypothesis were true.
c. The actual counts that did occur in the observed data.
d. The long-run counts that would be expected if the observed counts are representative.
14. Pick the choice that best completes the following sentence. If a relationship between two
variables is called statistically significant, it means the investigators think the variables are
a. related in the population represented by the sample.
b. not related in the population represented by the sample.
c. related in the sample due to chance alone.
d. very important.
15. Simpson's Paradox occurs when
a. No baseline risk is given, so it is not know whether or not a high relative risk has practical importance.
b. A confounding variable rather than the explanatory variable is responsible for a change in the response variable.
c. The direction of the relationship between two variables changes when the categories of a confounding variable are taken into account.
d. The results of a test are statistically significant but are really due to chance.
