Question

n a cognitive psychology experiment, the researcher is interested in whether encoding condition has a significant effect on memory for a list of words. She recruits subjects to participate in the experiment. Each recruited subject is randomly assigned to either encoding condition A or encoding condition B. The researcher would like to leave the hypothesis non-directional without predicting which encoding condition would lead to better memory, and she sets the significance level at α = .05 for a two-tailed test.

Hint: You may remember a similar scenario in the previous assignment, but with a crucial difference. In the previous assignment, each subject attends BOTH condition A and condition B, while each subject here attends only ONE condition (either A or B).

Subject ID	Encoding A		Subject ID	Encoding B
1	87		11	85
2	80		12	80
3	78		13	76
4	76		14	77
5	86		15	86
6	77		16	68
7	83		17	85
8	82		18	79
9	91		19	89
10	90		20	85

1. Calculate the T statistic

2.For the two-tailed test, find the critical t values for this hypothesis test based on the total degree of freedom (from question d above), and the preset alpha level

3.Calculate the pooled standard deviation for the populations (use the pooled variance calculated in question f); and then calculate the standardized effect size of this test

4.Draw a conclusion based on the hypothesis test result and the effect size. In other words, did encoding condition have a significant effect on memory score? Was the effect small, medium, or large?

Answer 1

Ans.

We find Sample standard deviations of both conditions using R:-

>Encoding_A<-c(87,80,78,76,86,77,83,82,91,90)

>mean(Encoding_A)

[1] 83

>sd(Encoding_A)

[1] 5.354126

>Encoding_B<-c(85,80,76,77,86,68,85,79,89,85)

>mean(Encoding_B)

[1] 81

>sd(Encoding_B)

[1] 6.253888