invest_3ed.pdf

# 65 with a clinical diagnosis of mild to moderate

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65 with a clinical diagnosis of mild to moderate depression (who would apply for such a study and fit the inclusion criteria) will have a higher probability of substantially reducing their depression symptoms if they are allowed to swim with dolphins rather than simply visiting and swimming in Honduras. Because this was a randomized comparative experiment, we can conclude that there is moderately strong evidence that swimming with dolphins causes a higher probability of experiencing substantial improvement in depression symptoms. But with this volunteer sample, we should be cautious about generalizing this conclusion beyond the population of people suffering from mild-to- moderate depression who could afford to take the time to travel to Honduras for two weeks. Practice Problem 3.6A A recent study compared two groups: One group was reminded of the sacrifices that physicians have to make as part of their training, and the other group was given no such reminder. All physicians in the study were then asked whether they consider it acceptable for physicians to receive free gifts from industry representatives. It turned out that 57/120 in the “sacrifice reminders” group answered that gifts are acceptable, compared to 13/60 in the “no reminder” group. (a) Identify the explanatory and response variables in this study. (b) Do you believe this study used random assignment? What would that involve? (c) Do you believe this study used random sampling? What would that involve? (d) Explain how you would carry out a simulation analysis to approximate a p-value for this study. [ Hint : How many cards? How many of each type? How many would you deal out? What would you record? How would you find the p-value?] (e) A colleague points out that the sample sizes are not equal in this study, so we can’t dr aw meaningful conclusions. How should you respond? Practice Problem 3.6B How would you find a two-sided p-value for the dolphin study?

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Chance/Rossman, 2015 ISCAM III Investigation 3.7 216 Investigation 3.7: Is Yawning Contagious? The folks at MythBusters , a popular television program on the Discovery Channel, investigated whether yawning is contagious by recruiting fifty subjects at a local flea market and asking them to sit in one of three small rooms for a short period of time. For some of the subjects, the attendee yawned while leading them to the room (planting a yawn “seed”), whereas for other subjects the attendee did not yawn. As time passed, the researchers watched (via a hidden camera) to see which subjects yawned. (a) Identify the explanatory variable (EV) and the response variable (RV) in this study. EV: RV: (b) Define the relevant parameter of interest, and state the null and alternative hypotheses for this study. Be sure to clearly define any symbols that you use.
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