In a cognitive psychology experiment, the researcher isinterested in whether encoding condition has an effect on memoryfor a list of words. She recruits 16 subjects to participate in theexperiment. Each subject comes to the lab twice to be tested in twodifferent encoding conditions and their memory performance scoresare listed below. The researcher would like to leave the hypothesisnon-directional without predicting which encoding condition wouldlead to better memory, and she sets the significance level at α =.05 for a two-tailed test.
Subject ID | Encoding A | Encoding B |
1 | 87 | 85 |
2 | 80 | 81 |
3 | 80 | 76 |
4 | 76 | 78 |
5 | 86 | 87 |
6 | 78 | 68 |
7 | 83 | 85 |
8 | 82 | 79 |
9 | 92 | 90 |
10 | 90 | 85 |
11 | 80 | 81 |
12 | 80 | 76 |
13 | 76 | 78 |
14 | 89 | 87 |
15 | 80 | 79 |
16 | 90 | 90 |
a. Identify the dependent variable (this is the outcome measure)and the independent variable (this is what differentiates the twogroups of data points being compared). (1 point total: .5 for DV,.5 for IV)
b. What would be the null and alternative hypotheses in bothwords and symbol notations? (2 points total: 1 for each hypothesis,.5 for written and .5 for notation)
Perform the steps below to get the t statistic for thesample:
c. Calculate the difference scores and enter them into the tablebelow. (1 point, deduct .5 for each error up to 1 point total)
Subject ID | Difference |
1 | |
2 | |
3 | |
4 | |
5 | |
6 | |
7 | |
8 | |
9 | |
10 | |
11 | |
12 | |
13 | |
14 | |
15 | |
16 | |
d. Mean of sample (1 point: .5 if process is correct but answeris wrong)
e. Estimated population standard deviation (1 point: .5 ifprocess is correct but answer is wrong)
f. Standard error (1 point: .5 if process is correct but answeris wrong)
g. Calculated t statistic (1 point: .5 if process iscorrect but answer is wrong)
With the calculated t statistic, perform the following steps toconclude the hypothesis test.
h. Critical t value (1 point: .5 if process is correctbut answer is wrong)
i. Compare the t statistic with the critical tvalue. Is the calculated t statistic more extreme or lessextreme than the critical t value? Then make a decisionabout the hypothesis test, stating explicitly “reject†or “fail toreject†accordingly. (1 points total: .5 for each answer)
j. Interpret the result in 1-2 sentences to answer the researchquestion (you may use the wording from the hypothesis or explain itin your own words) (1 point)
k. Calculate the standardized effect size of this hypothesistest (1 point: .5 if process is correct but answer is wrong)
