T Tests Application, unit 8 assignment help
Subject
Humanities
Question Description
UNIT 8
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T Tests: Application
INTRODUCTION
In Unit 8, we will apply our understanding of t tests in an IBM SPSS assignment. As in Unit 6, you will use the Data Analysis and Application (DAA) Template to submit your assignment.TOGGLE DRAWERHIDE FULL INTRODUCTION
TESTING ASSUMPTIONS: THE SHAPIRO-WILK TEST AND THE LEVENE TEST
Recall from Unit 7 that two assumptions of the t test are that:
The outcome variable Y is normally distributed.
The variance of Y scores is approximately equal across groups (homogeneity of variance assumption).
THE SHAPIRO-WILK TEST
In addition to a visual inspection of histograms and calculation of skewness and kurtosis values, SPSS provides a formal statistical test of normality referred to as the Shapiro-Wilk test. A perfect normal distribution will have a Shapiro-Wilk value of 1.00. Values less than 1.00 indicate an increasing departure from a perfect normal shape. The null hypothesis of the Shapiro-Wilk test is that the distribution is normal. When the Shapiro-Wilk test indicates a p value less than .05, the normality assumption may be violated, which can be problematic.To obtain the Shapiro-Wilk test in SPSS, follow the step-by-step guide for t tests that is provided in the Unit 8 assignment. SPSS provides the Shapiro-Wilk test output for interpretation. A significant Shapiro-Wilk test ( p < .05) suggests that the distribution is not normal and interpretations may be affected. However, the t test is fairly robust to violations of this assumption when sample sizes are sufficiently large (that is, greater than 100 members).