Discussion: Estimating Models Using Dummy Variables
You have had plenty of opportunity to interpret coefficients for metric variables in regression models. Using and interpreting categorical variables takes just a little bit of extra practice. In this Discussion, you will have the opportunity to practice how to recode categorical variables so they can be used in a regression model and how to properly interpret the coefficients. Additionally, you will gain some practice in running diagnostics and identifying any potential problems with the model.
To prepare for this Discussion:
- Create a research question using the General Social Survey dataset that can be answered by multiple regression. Using the SPSS software, choose a categorical variable to dummy code as one of your predictor variables.
By Day 3
Estimate a multiple regression model that answers your research question. Post your response to the following:
- What is your research question?
- Interpret the coefficients for the model, specifically commenting on the dummy variable.
- Run diagnostics for the regression model. Does the model meet all of the assumptions? Be sure and comment on what assumptions were not met and the possible implications. Is there any possible remedy for one the assumption violations?
Be sure to support your Main Post and Response Post with reference to the week’s Learning Resources and other scholarly evidence in APA Style.
Note from Professor on how to complete discussion requirement:
“Use the General Social Survey (GSS) dataset for this Assignment
Identify 2 independent variables (IV1 and IV2) and their Level of Measurement. The IV1 and IV2 can be interval, ratio, nominal, or ordinal.
Identify the dependent variable (DV) and its Level of Measurement. The DV must be interval or ratio.
Write a research question for multiple regression. Use this format:
What is the relationship between IV1 and IV2s (state the IVs) and the DV (state the DV)?
Write the null hypothesis. Use this format:
-There is no relationship between IV1 and IV2 and the DV.
State the research design.
Use SPSS to answer the research question. Here’s how:
- Open the GSS data set, select Analyze, select Regression, Select Linear, drag IV1 and IV2 into the Independent(s) box and the DV into the Dependent box, and click OK.
- Review the Sig. value in the SPSS Output under ANOVA and decide to reject or fail to reject the null hypothesis.
- If you reject the null and determine that the ANOVA is statistically significant, report and explain the effect size. Effect size is found under R square in the Model Summary.
- If you fail to reject the null hypothesis, select new variables and repeat 1-3 steps above.
Write the regression equation. Here’s how:
Examine the Coefficients output and identify the Constant value under Unstandardized Coefficients in column B and the coefficient values for IV1 and IV2 directly below the Constant value. Write your regression equation in this format:
DV = Constant value + IV1(coefficient value) + IV2(coefficient value), but substitute the names of IV1, IV2 and the DV and the actual Constant value and coefficient value for IV1 and IV2. Here’s an example:
If Socioeconomic Status is the DV, Age is IV1 and Highest Degree is IV2, then your equation could look like this:
Socioeconomic status = 15 + (.114)(Age) + (11.3)(Highest Degree)
Do not use these numbers. Do your own calculations
Discuss implications for social change”