© Copyright 2000, Julia Hartman 1 An Interactive Tutorial for SPSS 10.0 for Windows © Analysis of Covariance (GLM Approach) by Julia Hartman Next

© Copyright 2000, Julia Hartman 2 ANCOVA (GLM): Introduction Analysis of Covariance (ANCOVA) is used: To assess the joint significance of predictors on a continuous outcome (GLM approach) To generate prediction equations for various levels of a categorical predictor (regression approach) Next

© Copyright 2000, Julia Hartman 3 ANCOVA (GLM): Introduction This tutorial uses the General Linear Model (GLM) approach to ANCOVA to determine whether MCAT scores are significantly different among medical students who had different types of undergraduate majors, when adjusted for year of matriculation. Next

© Copyright 2000, Julia Hartman 4 Dependent variable  nmtot1: MCAT total (most recent) Fixed factor  bmaj2: Undergraduate major 1 = Biology/Chemistry 2 = Other science/health 3 = Other Covariate  matyr: Year of matriculation Next ANCOVA (GLM): Introduction

© Copyright 2000, Julia Hartman 5 ANCOVA (GLM): Starting the Procedure In the menu, click Analyze

© Copyright 2000, Julia Hartman 6 ANCOVA (GLM): Starting the Procedure In the menu, click on Analyze Point to General Linear Model

© Copyright 2000, Julia Hartman 7 ANCOVA (GLM): Starting the Procedure In the menu, click on Analyze Point to General Linear Model Point to Univariate…

© Copyright 2000, Julia Hartman 8 ANCOVA (GLM): Starting the Procedure In the menu, click on Analyze Point to General Linear Model Point to Univariate… … and click.

© Copyright 2000, Julia Hartman 9 ANCOVA (GLM): Selecting Variables Choose the variables for analysis from the list in the variable box. For this tutorial, begin by scrolling down the variable list.

© Copyright 2000, Julia Hartman 10 Point to the variable labeled Undergraduate Major [bmaj2] ANCOVA (GLM): Selecting Variables

© Copyright 2000, Julia Hartman 11 Point to the variable labeled Undergraduate Major [bmaj2] …and click. ANCOVA (GLM): Selecting Variables

© Copyright 2000, Julia Hartman 12 Move bmaj2, a categorical variable, to the box labeled Fixed Factor(s) by clicking the arrow. ANCOVA (GLM): Selecting Variables

© Copyright 2000, Julia Hartman 13 Scroll back up the list, ANCOVA (GLM): Selecting Variables

© Copyright 2000, Julia Hartman 14 Scroll back up the list, point to the variable nmtot1, which is labeled MCAT TOTAL 1992-PRESENT, MOST RECENT ANCOVA (GLM): Selecting Variables

© Copyright 2000, Julia Hartman 15 …and click. Scroll back up the list, point to the variable nmtot1, which is labeled MCAT TOTAL 1992-PRESENT, MOST RECENT ANCOVA (GLM): Selecting Variables

© Copyright 2000, Julia Hartman 16 Move nmtot1, a continuous variable, to the box labeled Dependent Variable by clicking the arrow. ANCOVA (GLM): Selecting Variables

© Copyright 2000, Julia Hartman 17 Scroll to the top of the list ANCOVA (GLM): Selecting Variables

© Copyright 2000, Julia Hartman 18 Scroll to the top of the list, and click the variable matyr, which is labeled MATRICULATION DATE. ANCOVA (GLM): Selecting Variables

© Copyright 2000, Julia Hartman 19 Move matyr, another continuous variable, to the box labeled Covariate(s) by clicking the arrow. ANCOVA (GLM): Selecting Variables

© Copyright 2000, Julia Hartman 20 ANCOVA (GLM): Profile Plots Request profile plots of estimated marginal means by clicking the button labeled Plots…

© Copyright 2000, Julia Hartman 21 This tutorial requests a profile plot of matyr*bmaj2. Click matyr in the Factors box. ANCOVA (GLM): Profile Plots

© Copyright 2000, Julia Hartman 22 Move matyr to the Horizontal Axis box by clicking the arrow. ANCOVA (GLM): Profile Plots

© Copyright 2000, Julia Hartman 23 Now click bmaj2 in the Factors box … ANCOVA (GLM): Profile Plots

© Copyright 2000, Julia Hartman 24 and move it to the Separate Lines box by clicking the arrow. ANCOVA (GLM): Profile Plots

© Copyright 2000, Julia Hartman 25 Click the Add button to request the plot. ANCOVA (GLM): Profile Plots

© Copyright 2000, Julia Hartman 26 Click the Continue button. ANCOVA (GLM): Profile Plots

© Copyright 2000, Julia Hartman 27 ANCOVA (GLM): Post Hoc Multiple Comparisons To request post hoc tests for pairwise multiple comparisons, click the Post Hoc… button.

© Copyright 2000, Julia Hartman 28 Comparisons are available for the categorical variable bmaj2 only. Click bmaj2 in the Factor(s) box. ANCOVA (GLM): Post Hoc Multiple Comparisons

© Copyright 2000, Julia Hartman 29 Move bmaj2 to the Post Hoc Tests for: box by clicking the arrow. ANCOVA (GLM): Post Hoc Multiple Comparisons

© Copyright 2000, Julia Hartman 30 Request multiple comparison test(s) by clicking in the corresponding checkbox. For this tutorial, click Bonferroni. ANCOVA (GLM): Post Hoc Multiple Comparisons

© Copyright 2000, Julia Hartman 31 In SPSS, you can request as many multiple comparison tests as you want. To continue the tutorial, click the Continue button. ANCOVA (GLM): Post Hoc Multiple Comparisons

© Copyright 2000, Julia Hartman 32 ANCOVA (GLM): Optional Descriptive Statistics To display estimated marginal means, parameter estimates, and descriptive and diagnostic statistics, or to change the alpha level, click the Options… button.

© Copyright 2000, Julia Hartman 33 ANCOVA (GLM): Options: Estimated Marginal Means You can request an overall (grand) marginal mean, as well as marginal means for the factors and the interaction(s). For this tutorial, click bmaj2.

© Copyright 2000, Julia Hartman 34 ANCOVA (GLM): Options: Estimated Marginal Means Click the arrow to move bmaj2 to the Display Means for: box.

© Copyright 2000, Julia Hartman 35 ANCOVA (GLM): Selecting Options Request other options by clicking the appropriate checkbox. In the Display area, click the checkbox for Descriptive statistics …

© Copyright 2000, Julia Hartman 36 …and the one for Homogeneity tests. ANCOVA (GLM): Selecting Options

© Copyright 2000, Julia Hartman 37 This tutorial uses no more options, so click the Continue button. ANCOVA (GLM): Selecting Options

© Copyright 2000, Julia Hartman 38 ANCOVA (GLM): Run the analysis Click the OK button to run the ANCOVA (GLM).

© Copyright 2000, Julia Hartman 39 ANCOVA (GLM) Output: General Information The labels and format of your output may be somewhat different. Next

© Copyright 2000, Julia Hartman 40 ANCOVA (GLM) Output: : Descriptive Statistics Next Previous

© Copyright 2000, Julia Hartman 41 ANCOVA (GLM) Output: : Descriptive Statistics (continued) Next Previous

© Copyright 2000, Julia Hartman 42 ANCOVA (GLM) Output: Test of Equality of Error Variances Next Previous

© Copyright 2000, Julia Hartman 43 ANCOVA (GLM) Output: Tests of Between-Subjects Effects Next Previous

© Copyright 2000, Julia Hartman 44 ANCOVA (GLM) Output: Expected Mean Squares Next Previous

© Copyright 2000, Julia Hartman 45 ANCOVA (GLM): Estimated Marginal Means: Undergraduate Major Next Previous

© Copyright 2000, Julia Hartman 46 ANCOVA (GLM): Post Hoc Tests: Undergraduate Major Next Previous

© Copyright 2000, Julia Hartman 47 ANCOVA (GLM): Profile Plot: Gender*Resloc Next Previous

© Copyright 2000, Julia Hartman 48 An Interactive Tutorial for SPSS 10.0 for Windows © : ANCOVA (GLM) Repeat this tutorial Click one of the following: Return to the list of tutorials