Question

Identifying individuals with a high risk of Alzheimer’s disease usually involves a long series of cognitive tests. However, researchers have developed a 7-Minute Screen, which is a quick and easy way to accomplish the same goal. The question is whether the 7-Minute Screen is as effective as the complete series of tests. To address this question, Ijuin et al. (2008) administered both tests to a group of patients and compared the results. The following data represent results similar to those obtained in the study.

Patient	7-Minute Screen		Cognitive Series
A	3	11
B	8	19
C	10	22
D	8	20
E	4	14
F	7	13
G	4	9
H	5	20
I	14	25

A. Compute the Pearson Correlation Coefficient for these data.

r =

B. The correlation is

Medium and negative

Large and negative

Large and positive

Medium and positive

C. The null hypothesis for a two-tailed test is

The correlation between the scores on the 7-minute screen test and the scores on the cognitive series is significant

The correlation between the scores on the 7-minute screen test and the scores on the cognitive series is not significant

The correlation between the scores on the 7-minute screen test and the scores on the cognitive series is less than zero

The correlation between the scores on the 7-minute screen test and the scores on the cognitive series is different from zero

D. If we use a two-tailed test with α = .01, the critical r values are:

±0.666

±0.582

±0.798

±0.750

E. Your decision is:

Reject the null hypothesis and conclude that there is a significant correlation between the scores on the 7-minute screen test and the scores on the cognitive series

Fail to reject the null hypothesis and conclude that there is a significant correlation between the scores on the 7-minute screen test and the scores on the cognitive series

Reject the null hypothesis and conclude that there is no significant correlation between the scores on the 7-minute screen test and the scores on the cognitive series

Fail to reject the null hypothesis and conclude that there is no significant correlation between the scores on the 7-minute screen test and the scores on the cognitive series

Answer 1

correlation coefficient r=

Sxy/(√Sxx*Syy) =

0.8351

Large and positive

c)The correlation between the scores on the 7-minute screen test and the scores on the cognitive series is not significant
d)

±0.798

e)Reject the null hypothesis and conclude that there is a significant correlation between the scores on the 7-minute screen test and the scores on the cognitive series