Question

An educational psychologist wants to check claims that regular physical exercise improves academic achievement. To control for academic aptitude, pairs of college students with similar GPAs are randomly assigned to either a treatment group that attends daily exercise classes or a control group. At the end of the experiment, the following scores were reported for the six pairs of participants:

Pair Number Phyasical excercise(X1) No Physical excercise(X2)
1 4.00 3.75
2 2.67 2.74
3 3.65 3.42
4 2.11 1.67
5 3.21 3.00
6 3.60 3.25
7 2.80 2.65

a. Using t, test the null hypothesis at the .01 level of significance.
b. Specify the p-value for this test result.
c. If appropriate (because the test result is statistically significant), use Cohen's d to estimate the effect size.
d. How might this test result be reported in the literature?

Answer 1

a. We fail to reject the null hypothesis

b. p > 0.01

c. The test result is not statistically significant

d. There not is enough statistical evidence to suggest that regular exercise improves academic achievement

Explanation:

No. Physical Exercise (X₂); 3.75, 2.74, 3.42, 1.67, 3, 3.25, 2.65

Physical Exercise (X₁); 4.00, 2.67, 3.65, 2.11, 3.21, 3.60, 2.80

GPAs Pair number; 1, 2, 3, 4, 5, 6, 7

The null hypothesis, H₀; μ₁ ≤ μ₂

The alternative hypothesis, Hₐ; μ₁ > μ₂

From the data, we have;

`\overline d` ≈ 0.222857

Where;

d = X₁ - X₂

`\overline d = (1)/(n) * \sum_(i = 1)^(n) d_i`

Similarly, we have;

`s_d^2=(\sum \left (d-\overline d \right )^(2) )/(n - 1)`

From which we get;

`s_d` ≈ 0.160905

The critical-t at n - 1 = 7 - 1 = 6 degrees of freedom for α = 1% = 0.01, is given as follows;

`t_(\alpha /2)` =
`t_((0.005, \, 6))` = 3.707

The test statistic, t =
`\overline d`/(
`s_d`/√n)

∴ t = 0.222857/(0.160905/√7) ≈ 3.664

The test statistic , t ≈ 3.664

Therefore, given that the test statistic is smaller than the critical-t,

b. The p-value estimate is p > 0.01

c. The test result is not statistically significant

d. The test result can be reported in a literature as that there is not enough statistical evidence to reject the null hypothesis, therefore, there not is enough statistical evidence to suggest that regular exercise improves academic achievement