invest_3ed.pdf

# The researchers could try the study again with a

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truly larger when a yawn seed is planted. The researchers could try the study again with a larger sample size to increase the power of their test. The researchers also may want to be cautious in generalizing these results beyond the population of volunteers at a local flea market. It’s also not clear how naturalistic the setting of leading individuals to a small room to wait is.

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Chance/Rossman, 2015 ISCAM III Investigation 3.7 222 Practice Problem 3.7A (a) For the Mythbusters’ study (p -value > 0.5), is it reasonable to conclude from this study that we have strong evidence that yawning is not contagious? Explain. (b) Explain, in this context, what is meant in the Study Conclusions box by “the researchers could try the study again with a larger sample size to increase the power of their test” and why that is a reasonable recommendation here. (c) To calculate the p-value here, why are we using the hypergeometric distribution instead of the binomial distribution? Practice Problem 3.7B Reconsider the Dolphin Therapy study (Investigation 3.6). Dolphin Therapy Control Group Total Showed substantial improvement 10 3 13 Did not show substantial improvement 5 12 17 Total 15 15 30 Continue to focus on the number of improvers randomly assigned to the dolphin group, and represent this value by X. (a) When the null hypothesis is true, the random variable X has a hypergeometric distribution. Specify the values of N , M , and n . (b) Calculating the exact p-value involves finding P(X __________). [ Hint : Fill in the blank with an inequality symbol and a number.] (c) Calculate this exact p-value, either by hand or with technology. Comment on whether this p-value is similar to the approximate one from your simulation results. (Be sure it’s clear how you calculated this value.) (d) Suppose that the dolphin study had involved twice as many subjects, again with half randomly assigned to each group, and with the same proportion of improvers in each group. Determine the exact p-value in this case, and comment on whether/how it changes from the p-value with the real data. Explain why this makes sense.
Chance/Rossman, 2015 ISCAM III Investigation 3.8 223 Investigation 3.8: CPR vs. Chest Compressions For many years, if a person experienced a heart attack and a bystander called 911, the dispatcher instructed the bystander in how to administer chest compression plus mouth-to-mouth ventilation (a combination known as CPR) until the emergency team arrived. Some researchers believe that giving instruction in chest compression alone (CC) would be a more effective approach. In the 1990s, a randomized study was conducted in Seattle involving 518 cases (Hallstrom, Cobb, Johnson, & Copass, New England Journal of Medicine , 2000). In 278 cases, the dispatcher gave instructions in standard CPR to the bystander, and in the remaining 240 cases the dispatcher gave instructions in CC alone. A total of 64 patients survived to discharge from the hospital: 29 in the CPR group and 35 in the CC group.

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