homogeneity of slopes

  1. N

    Significant treatment*pretest interaction, but interaction not shown with regression lines

    Hello, I have found that the interaction treatment by pretest is significant. However, the interaction is not depicted on the scatterplot (see attachments). Am I doing something wrong or can I say that the interaction is outside the range of possible test scores (0-10) and that the assumption...
  2. T

    ANCOVA with more than 2 covariates. homogeneity of regression slopes.

    Hello, I am carrying out a ANCOVA with more than 2 covariates with SPSS. I want to check the homogeneity of regression slopes to confirm the assumption. When in a ANCOVA with one covariates, I can understand. https://www.youtube.com/watch?v=oNX8hL6QHNM When in a ANCOVA with more than 2...
  3. M

    Assumptions in ANCOVA, and consequences of violating them

    I ran an ANOVA with 4 predictors (2 categorical, 2 continuous) and 1 covariate (continuous). Including the covariate did not significantly alter the main effects of the ANOVA when it was run without the covariate, so I concluded that the covariate did not need to be included in the overall...
  4. S

    Homogeneity of regression slopes

    If assumption of homogeneity of regression slopes broken in ANCOVA analysis, what to do? Can I use linear regression instead? Thanks