Dr Z conducts a study in which two groups of participants ar

Dr. Z conducts a study in which two groups of participants are compared on a measure of neuroticism. Participants are divided into two groups based on age (under 40 and over 40,) then complete a standardized measure of neuroticism. On the basis of this output for an independent sample t-test, answer the following questions. Assume alpha = .05. NOTE: in order to save space, I have omitted the Levene’s test. Assume that variances are equal.

State the decision you would reach (i.e., reject or fail to reject the null).

In words, interpret the 95% confidence interval.

Group Statistics

age

N

Mean

Std. Deviation

Std. Error Mean

neuroticism

under 40

17

18.40

10.15

2.52

over 40

20

25.42

9.38

3.11

Independent Samples Test

t-test for Equality of Means

t

df

Sig. (2-tailed)

Mean Difference

Std. Error Difference

95% Confidence Interval of the Difference

Lower

Upper

neuroticism

Equal variances assumed

3.11

35

.001

7.02

2.26

3.92

10.12

Solution

Since the P value is 0.001 which is less than alpha=0.05, thus reject the null hypothesis.

Hence the test is statistically significant.

The 95% Confidence interval is: (3.92,10.12)

The above interval holds the true mean difference with 95% confidence.