Question

Consult the t-table and r-table and indicate the exact critical value of t or r that you would use for each of the following statistical tests. Pull the exact value out of the table without rounding it. You will need to determine which test each study would use in order to correctly identify each df.

a. Depression score data from 15 participants were collected both before and after they each took an antidepressant. You use a two-tailed test t-test with an alpha of .05 to examine the effects of the drug.

b. Twenty-two participants were randomly split into two groups of 11, one of which took an antidepressant and one of which served as a control group. You use a one-tailed test with an alpha of .05 to examine the effects of the drug on depression scores.

c. You use a two-tailed test with an alpha of .01 to compare the mean depression score of 9 participants to the population mean.

d. You gather 9 participants, assess their self-esteem and depression scores and examine whether self-esteem is negatively correlated with depression. You use a one-tailed test with an alpha of .01.

Answer 1

(a)

n = 15

df = 15 - 1 = 14

Two Tail Test

= 0.05

From Table, critical values of t = 2.1448

So,

Answer is:

2.1448

(b)

n1 = 11

n2 = 11

df = 11 + 11 - 2 = 20

One Tail Test

= 0.05

From Table, critical values of t = 1.7247

So,

Answer is:

1.7247

(c)

n = 9

df = 9 - 1 = 8

Two Tail Test

= 0.01

From Table, critical values of t = 3.3554

So,

Answer is:

3.3554

(d)

n = 9

df = 9 - 2 = 7

One Tail Test

= 0.01

From Table, critical values of t = - 2.9980

So,

Answer is:

- 2.9980