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Stop doing homework! (4.3)Researchers in Spain interviewed 772513-year-olds about their homework habits—how much time they spent per night on homework and whether they got help from their parents or not—and then had them take a test with 24math questions and 24science questions. They found that students who spent between 90and 100minutes on homework did only a little better on the test than those who spent 60to 70minutes on homework. Beyond 100minutes, students who spent more time did worse than those who spent less time. The researchers concluded that 60to 70minutes per night is the optimum time for students to spend on homework.32 Is it appropriate to conclude that students who reduce their homework time from 120minutes to 70minutes will likely improve their performance on tests such as those used in this study? Why or why not? independent random samples from two populations of interest or from two groups in a randomized experiment, use two-sample t procedures for μ1−μ23051526=0.200=20.0%μ1-μ2

Short Answer

Expert verified

The required answer is No

Step by step solution

01

Explanation

In the previous exercise, we concluded that there was a link between homework time and test performance, such as those used in the study, because homework times longer than 100minutes tend to correspond with poor test results.

However, association does not imply causation, which means that reducing homework time does not always result in better test results.

02

For example

It is possible that people with long homework times have learning difficulties, and that reducing their homework time will worsen their test results.

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Most popular questions from this chapter

A random sample of size nwill be selected from a population, and the proportion of those in the sample who have a Facebook page will be calculated. How would the margin of error for a 95%confidence interval be affected if the sample size were increased from 50to 200?

(a) It remains the same.

(b) It is multiplied by 2.

(c) It is multiplied by 4.

(d) It is divided by 2.

(e) It is divided by 4.

Suppose the probability that a softball player gets a hit in any single at-bat is 0.300. Assuming that her chance of getting a hit on a particular time at bat is independent of her other times at bat, what is the probability that she will not get a hit until her fourth time at bat in a game?

a.(43)(0.3)1(0.7)33051526=0.200=20.0%43(0.3)1(0.7)3

b.(43)(0.3)3(0.7)13051526=0.200=20.0%43(0.3)3(0.7)1

C.(41)(0.3)3(0.7)13051526=0.200=20.0%41(0.3)3(0.7)1

d.(0.3)3(0.7)13051526=0.200=20.0%(0.3)3(0.7)1

e.(0.3)1(0.7)33051526=0.200=20.0%(0.3)1(0.7)3

Does drying barley seeds in a kiln increase the yield of barley? A famous

experiment by William S. Gosset (who discovered the t distributions) investigated this

question. Eleven pairs of adjacent plots were marked out in a large field. For each pair,

regular barley seeds were planted in one plot and kiln-dried seeds were planted in the

other. A coin flip was used to determine which plot in each pair got the regular barley seed

and which got the kiln-dried seed. The following table displays the data on barley yield

(pound per acre) for each plot.

Do these data provide convincing evidence at the α=0.05 level

that drying barley seeds in a kiln increases the yield of barley, on average?

Which inference method?

a. Drowning in bathtubs is a major cause of death in children less than5years old. A random sample of parents was asked many questions related to bathtub safety. Overall,85%of the sample said they used baby bathtubs for infants. Estimate the percent of all parents of young children who use baby bathtubs.

b. How seriously do people view speeding in comparison with other annoying behaviors? A large random sample of adults was asked to rate a number of behaviors on a scale of1(no problem at all) to5(very severe problem). Do speeding drivers get a higher average rating than noisy neighbors?

c. You have data from interviews with a random sample of students who failed to graduate from a particular college in7years and also from a random sample of students who entered at the same time and did graduate within7years. You will use these data to estimate the difference in the percent's of students from rural backgrounds among dropouts and graduates.

d. Do experienced computer-game players earn higher scores when they play with someone present to cheer them on or when they play alone? Fifty teenagers with experience playing a particular computer game have volunteered for a study. We randomly assign25 of them to play the game alone and the other25to play the game with a supporter present. Each player’s score is recorded.

The P-value for the stated hypotheses is 0.002Interpret this value in the context of this study.

a. Assuming that the true mean road rage score is the same for males and females, there is a 0.002probability of getting a difference in sample means equal to the one observed in this study.

b. Assuming that the true mean road rage score is the same for males and females, there is a 0.002 probability of getting a difference in sample means at least as large in either direction as the one observed in this study.

c. Assuming that the true mean road rage score is different for males and females, there is a 0.002 probability of getting a difference in sample means at least as large in either direction as the one observed in this study.

d. Assuming that the true mean road rage score is the same for males and females, there is a 0.002 probability that the null hypothesis is true.

e. Assuming that the true mean road rage score is the same for males and females, there is a 0.002 probability that the alternative hypothesis is true.

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