Part 2 of SPSS

This worksheet was developed by Dr. Kurt Michael of Liberty University © 2015 Page 1 of 5

Name:

SPSS Worksheet 1: (t-test)

Instructions: Lesson 24 Exercise File 1 is located at the end of the chapter under the heading Exercises in your Green and Salkind textbook. Complete the exercise and then complete the worksheet below by filling in the blanks and answering the questions.

H01: There is no significant difference in the amount of time it takes to eat a Big Mac meal between overweigh and normal weight individuals.

Assumptions

Outliers: Create a Box and Whisker plot for each group. Hint: Graph > Legacy > Boxplot > Simple. Insert the Box and Whisker plot below: Note: Look for extreme outliers.

Fill in the blanks:

Groups	Outliers (Item #); if none, enter n/a	Are there any outliers?
Overweight	n/a	no
Normal	n/a	no

<Note: Remove any outliers from the dataset before continuing.>

Assumption of Normality: Run a normality test for each group. Hint: Begin by going to Analyze > Descriptive > Explore. See page 262. Insert the Tests of Normality table below:

Tests of Normality
	Weight classification	Kolmogorov-Smirnova	Shapiro-Wilk
		Statistic	df	Sig.	Statistic	df	Sig.
Time spent eating Big Mac specials in seconds	overweight	.237	10	.116	.907	10	.258
	normal weight	.085	30	.200*	.982	30	.871
a. Lilliefors Significance Correction *. This is a lower bound of the true significance.

Fill in the blanks:

Should you use a Shapiro-Wilks or Kolmogorov-Smirnov test? Why?

Answer: Since n<50 we use Shapiro -Wilks

Groups	Significance	Is the assumption of normality met?
Overweight	0.258	Yes
Normal	0.871	yes

Assumption of Equal Variance: Insert Levene's Test of Equality of Error Variancesa table(s) below:

Levene's Test of Equality of Error Variancesa
Dependent Variable:Time spent eating Big Mac specials in seconds
F	df1	df2	Sig.
2.745	1	38	.106
Tests the null hypothesis that the error variance of the dependent variable is equal across groups.
a. Design: Intercept + weight

Fill in the blanks:

Significance	Is the assumption of equal variance met?
0.106	yes

Results

Insert t-test for equality of Means table(s) below:

Independent Samples Test
	Levene's Test for Equality of Variances	t-test for Equality of Means
	F	Sig.	t	df	Sig. (2-tailed)	Mean Difference	Std. Error Difference	95% Confidence Interval of the Difference
								Lower	Upper
Time spent eating Big Mac specials in seconds	Equal variances assumed	2.745	.106	-3.975	38	.000	-109.400	27.522	-165.116	-53.684
	Equal variances not assumed			-5.397	30.828	.000	-109.400	20.272	-150.754	-68.046

Fill in the blanks:

Equal variances assumed	Value
df	38
t- statistic	-3.975
t- critical (Hint: See Appendix B in Warner)	2.745
p- value	0.000
Eta Squared (Hint: See formula)	1.45

Is the t-statistic greater than t-critical?

Hint: Use the absolute value.

Answer: yes

Is the p-value less than .05?

Answer: yes

Should you reject or fail to reject the null?

Answer: reject

Is the effect size small, medium, or large? Hint: See Table 5.2 in Warner, p. 208.

Answer: small

Descriptive Statistics

Fill in the blanks:

Groups	M	SD
Overweight	589	42.615
Normal	698.4	82.949