4. Hypothesis testing with ANOVA Aa Aa Opinions about whether caffeine enhances

Question

4. Hypothesis testing with ANOVA Aa Aa Opinions about whether caffeine enhances test performance differ. You design a study to test the impact of drinks with different caffeine contents on students' test-taking abilities. You choose 21 students at random from your introductory psychology course to participate in your study. You randomly assign each student to one of three drinks, each with a different caffeine concentration, such that there are seven students assigned to each drink. You then give each of them a plain capsule containing the precise quantity of caffeine that would be consumed in their designated drink and have them take an arithmetic test 15 minutes later. The students receive the following arithmetic test scores: Coffee Water Espresso Caffeine Content (mg/oz) 13.4 51.3 2X2 142,493 78 92 83 G 723 88 87 83 N 21 72 80 76 72 89 79 64 96 86 81 83 79 82 92 81 T1 537 T2 619 T3 567 SS1 381.43 SS 85.7 SS 66 n1 n2 n3 M1 76.7143 M 88.4286 M3 81.0000 You plan to use an ANOVA to test the impact of drinks with different caffeine contents on students' test-taking abilities. What is the null hypothesis? O The population mean test scores for all three treatments are different. O The population mean test scores for all three treatments are not all equal. O The population mean test scores for all three treatments are equal. O The population mean test score for the water population is different from the population mean test score for the coffee population

Explanation / Answer

null hypothesis:the population mean test scores for all three treatments are equal

F ratio =MS between groups/MS with in

=245.90/35.17 =6.991

You can reject the null hypothesis, caffeine does appear to affect test performance.

Source of Variation SS df MS Between Groups 491.81 2 245.90 Within Groups 633.14 18 35.17 Total 1124.95 20

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