Homework 05

ANCOVA - Analysis of Covariance Exercise

For Homework 05, you will be using the HELP dataset, learn more at:

• https://melindahiggins2000.github.io/N736Fall2017_HELPdataset/ &
• https://github.com/melindahiggins2000/N736Fall2017_HELPdataset

Complete the following for these variables:

• OUTCOME VARIABLE (Y): indtot
• INDEPENDENT VARIABLE (X): mcs
• COVARIATES (other X’s): pss_fr or female

1. Run ANCOVA (using a regression, ANOVA, or GLM approach - your choice) for the association between the SF36 Mental Component Score (mcs) and Inventory of Drug Use (indtot) adjusting for perceived social support from friends (pss_fr). Remember to:
   • mean center continuous variables before computing the interaction term (i.e. create a new mean-centered variable by subtracting the mean)
   • check for the assumption of homogenity of variance (i.e. is the interaction term significant?)
   • make an “effects plot” plot of the interaction between mcs and pss_fr
2. Run ANCOVA (using a regression, ANOVA, or GLM approach - your choice) for the association between the SF36 Mental Component Score (mcs) and Inventory of Drug Use (indtot) adjusting for gender (female). Remember to:
   • mean center continuous variables before computing the interaction term (i.e. create a new mean-centered variable by subtracting the mean)
   • check for the assumption of homogenity of variance (i.e. is the interaction term significant?)
   • make an “effects plot” plot of the interaction between mcs and female