2022 Introduction to Statistics in Research Mitchell 2nd ed

I N T R O T O R E S E A R C H : D A T A V I S U A L I Z A T I O N & C O M M O N S T A T T E S T S

Table 110: SPSS Independent Samples Test Output

#1 - Example of Levene’s test: The illustration below shows the Levene’s test for equality of variance in SPSS. If the significance is above .05 (Illustration shows .174), you use the top row (Equality of variances assumed. Otherwise, use the second row. Notice the degrees of freedom in the second row is 15.123. SPSS adjusted the degree of freedom automatically using the Welch-Satterthwaite method.

#2 – Interpretation Choice -Compare calculated (absolute value) t to Critical Value (table)

The calculated t -value in the illustration below is 3.110. Compare this value to the critical value from a table using 18 degrees of freedom and an alpha level of .05. Make sure to understand which critical value table to use. If the critical value (table) is greater than the calculated t-value, reject the null hypothesis.

#3 – Interpretation Choice - Use the significance column.

The illustration shows .006 for significance. If the significance is less than .05, reject the null hypothesis and assume that the two group means as significantly different. This SPSS output shows the significance of a two tailed test. A one tailed test significance would be .003 calculated as follows (.006/2).

#4 – Understanding Confidence interval of the Difference.

This part compliments the significance test results. If the Confidence interval contains zero, the results are not significant at the chosen significance level. In this illustration, the 95% confidence interval is [3.244, 16.756], which does not contain zero. This agrees with the p -value of the significance test.

Use this information to answer the question:

Question 1: True or False: The results above suggest there is a probability of 1.3% for a Type 1 error.

Answer: True

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