Question

A group of individuals go on diet with a specific program that guarantees that you will lose weight with their program. Their weight is measured before the program and after. Did the diet significantly decrease their weight? (alpha =.05)

Post-Diet Weight (group 1)	Pre-Diet Weight (group 2)
150	160
150	200
180	220
170	190
160	170
190	190

Find the sum of the difference scores and the mean of the difference scores

		Σ=150 Mean of D=20
		Σ=130 Mean of D=21.67
		Σ= -130 Mean of D= -21.67
		Σ=150 Mean of D=21.67

Find the variance of the difference scores

		S2D = 846.20
		S2D = 376.67
		S2D = 500
		S2D = 4700

Find the standard error of the mean difference

		SD = 62.90
		SD = 376.67
		SD = 7.93
		SD = 15.00

What is the t-statistic?

		t = -2.73
		t = 7.93
		t = 2.80
		t = 2.15

What is the t-critical value?

		-2.571
		-2.015
		2.132
		1.943

What decision should you make about the null hypothesis?

		Fail to reject the null hypothesis, since the t-statistic is less than the t-critical value.
		Fail to reject the null hypothesis, since the t-statistic is greater than the t-critical
		Reject the null hypothesis, since the t-statistic is less than the t-critical.
		Reject the null hypothesis, since the t-statistic is greater than the t-critical.

Answer 1