Question

A researcher was interested in the effects of caffeine on sleep. She measured how many minutes it took for ten participants to fall asleep. Half of the participants drank a liter of caffeinated soda before going to sleep while the other half were only allowed to drink water. Summary data of minutes are presented below. Did the caffeine increase the length of time it took to fall asleep (a =.05)? (27 points total for 6a-e)

         Water Group Caffeine Group

                     18 22

                     15 15

                     19 20

                     14 21

                     14 19

a. Name the test to be conducted and why you selected it:

b. State the null and alternative hypotheses:

c. State the CV and the decision rule. Sketch the rejection region:

d. In SPSS, calculate the observed test statistic. Paste your answer here or attach it to your assignment. In addition, calculate the value of eta2 (h2).

e. Write out an APA style conclusion based on this finding:

Answer 1

Solution:

SPSS output for two-sample t-test. Note that, group_1 is Water group and group_2 is Caffeine group.

Conclusion:

From the output we can see the mean for Caffeine group i.e for group-2 is larger than group-1 water group.

P-value is greater than level of significance 0.05 therefore, we reject the null hypothesis of equality and conclude that there is significant difference between two groups. As the mean response for Caffeine group is larger we can state that Caffeine group increases the length of time to fall asleep.

Calculation of eta2: