In the famous “Doll Test” used by Kenneth Clark (1954), what factor is vitally important to control for to ensure that you don’t have a confounding variable associated with doll preferences?

Which of the following is an example of why we need descriptive measures in science when it comes to scientific record keeping?

The choice between a z-test and a t-test for a population mean depends primarily on:

Which of the following are false statements? I. Voluntary response samples often over-represent people with strong opinions. II. Samples that have not been selected randomly can be used for inference as long as a large enough sample is taken. III. Sophisticated statistical methods can always correct the results if the population you are sampling from is different from the population of interest, e.g. due to undercoverage.

Which of the following is NOT a theme of Way of the World?

A botanist is studying the petal lengths, measured in millimeters, of two species of lilies. The boxplots below illustrate the distribution of petal lengths from two samples of equal size, one from species A and the other from species B.  Based on these boxplots, which of the following is a correct conclusion about the data collected in this study?

A study of the effect of caffeine on muscle metabolism used eighteen male volunteers who each underwent arm exercise tests. Nine of the men were randomly selected to take a capsule containing pure caffeine one hour before the test. The other men received a placebo capsule. During each exercise the subject’s respiratory exchange ratio (RER) was measured. (RER is the ratio of CO2 produced to O2 consumed and is an indicator of whether energy is being obtained from carbohydrates or fats). Test the claim that the mean RER for the placebo group is different from the mean RER for the caffeine group. Use a 5% level of significance. Show all work for full credit.             Placebo                       Caffeine                                  108      101                              96        93        119      94                                99        88        100      95                                94        91        97        98                                89        88 93                                            86                      a. State the null and alternate hypotheses. b. Compute the test statistic. c. Find the critical value and/or the p value. d. Make a decision and justify it using the critical value and/or the p-value. e. Record an appropriate conclusion in context of this problem.

You roll a standard die one time. What is the classical (theoretical) probability of rolling a 4?

A manufacturer claims its Brand A battery lasts longer than its competitor’s Brand B battery. Nine batteries of each brand are tested independently, and the hours of battery life are shown below. Brand A      88   85   80   81   72   90   85   85   84 Brand B      80   79   77   82   75   81   77   73   78 Provided that the assumptions for inference are met, which of the following tests should be conducted to determine if Brand A batteries do, in fact, last longer than Brand B batteries?

In a purely symmetric distributions, what is the relationship between the mean and median?