ANALYZING DATA USING THE INDEPENDENT SAMPLES T-TEST
Please watch the “t-test video” and read the chapter’s SPSS demonstrations prior to doing the assigned exercise.
The legalization of marijuana is a topic being debated in many states throughout the U.S. Eight states, including MA, have now passed have some form of legal recreational marijuana use. The GSS2018 has a question [GRASS] which asks respondents if they support marijuana legalization. You want to explore whether these two groups–persons favoring legalization and persons opposing legalization—differ in terms of their age [age], years of education [educ], and number of children [childs].
The grouping (or independent) variable is GRASS—a dichotomous nominal variable. Your three testing (or dependent) variables are AGE, EDUC, CHILDS; all ratio variables.
You will conduct an independent samples t-test assuming a 2-tailed test with an alpha level of .05.
Step 1. Write the three null and alternative hypotheses.
Step 2. Run the SPSS analysis
- From the SPSS Menu baràANALYZEàCOMPARE MEANSàINDEPENDENT SAMPLES T-TEST
- In the independent samples t-test dialog box, enter your three testing or dependent variables in the test variable box—AGE, EDUC, and CHILDS.
- Now enter the grouping or independent variable—GRASS—into the grouping variable box. Question marks will appear.
- CLICKàDEFINE GROUPS; and a define groups dialog box will open.
- You must insert the value categories for GRASS (‘1’, and ‘2’), then CLICKàCONTINUE.
- CLICK the box next to “Estimate effect sizes” to get rid of the checkmark.
Step 3. Interpret the SPSS Output for the 3 hypotheses.
For each hypothesis:
- Read the GROUP STATISTICS BOX which gives each groups’ n’s, means and SD’s on your testing (dependent) variables
- Looking at the p value under the Levene’s test columns, determine whether the Levene’s test p value allows you to assume equal variances. This tells you whether to read the top or bottom row of the “t test for equality of means” section of the output.
- Note the t value, df and p-value.
- Make a decision about rejecting or retaining each null hypothesis.
Step 4. Write up the results
- Write up your results for each hypothesis separately. In doing so, be sure to provide support/evidence for your decision about rejecting or retaining the null hypothesis, including providing t-value, df, and p-value. Also report means and standard deviations for the two groups so that the reader can understand the specific nature of the differences (or lack of differences) between the two groups. When all is said and done, how do these two groups of adults (those who favor and oppose marijuana legalization) differ by age, education and number of children?
- Create a table that reports the results of the t test for GRASS and AGE with the essential numbers and statistical information: the means, SDs, t value, df, and p value.
An example for a write-up and table to report the results of a t test can be found in this week’s content. Refer also to articles that feature the t test for an example of how this can be done.
- NEED TO USE SPSS AND GSS DATA SET 2018 TO ANSWER AS WELL AS COPY AND PASTE ON SEPERATE PAGE SHOWING THE WORK IN SPSS