FAQ/anovaFAQ - CBU statistics Wiki

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FAQs for analysis of variance

  1. Why are the degrees of freedom not whole numbers?

  2. How do I compare a mean to a constant in EXCEL (one-sample t)?

  3. How do I calculate a 95% confidence interval for the group means from one-way ANOVAs (using either a within or between subjects factor)?

  4. How do I compute a t-test and F ratio using only summary measures in 2x2 between and within subjects ANOVA?

  5. A two-way analysis of variance to assess treatment and pre-test effects (Solomon's four group design)

  6. How do I work out degrees of freedom for terms in an ANOVA?

  7. What does a number containing an 'E' signify and how do I remove it?

  8. In ANOVA and Regression, what do the various different types of Sums of Squares mean, and does the choice matter?

  9. Can I use subjects as a random or fixed factor in an ANOVA?

  10. Sums of squares used by R in lm, lmer and aov

  11. A note about unequal group sizes in ANOVA

  12. A note about different sums of squares in unbalanced factorial ANOVAs

  13. What is the variance of the mean of my transformed data?

  14. What is the value of the error variance for raw data using that of its scalar transformed data?

  15. How do I format data for input into a repeated measures analysis in SPSS?

  16. What does the TRANSPOSE ALL DATA option in the RESTRUCTURE menu do in SPSS?

  17. Using the VARSTOCASES command in SPSS to convert repeated measures formatted data to a multilevel model format (and the CASESTOVARS command for the reverse operation).

  18. How do I perform a repeated measures analysis of variance in SPSS?

  19. How do I perform a repeated measures analysis of variance in SPSS involving repeated measures factors with more than 99 levels?

  20. How do I perform a repeated measures analysis of variance in R including correcting for sphericity?

  21. How do I perform a repeated measures analysis of variance in GENSTAT (and MATLAB)?

  22. How do I perform a repeated measures analysis of variance in MINITAB (and use this approach to obtain post-hoc tests on a repeated measures factor in SPSS)?

  23. How do I perform a non-standard comparison of means in a repeated measures anova in SPSS?

  24. What is the effect of dropping a between by within subjects interaction on other terms in a mixed anova?

  25. How do I work out the meaning of a significant interaction?

  26. How do I interpret a four-way interaction?

  27. Why don't I need to use a covariate which differs between randomised groups in an ANCOVA?

  28. Comparing ANCOVA to Repeated Measures ANOVA

  29. Can I do an analysis of covariance using a regression (including computation of covariate adjusted means) and use this to adjust for regression to the mean?

  30. ANCOVA versus Analysis of Residuals

  31. How do I handle errors in variables to estimate slopes and intercepts in a linear regression?

  32. Inappropriate use of a constant covariate in repeated measures ANCOVA

  33. How do I adjust for varying covariates in a repeated measures ANOVA in SPSS?

  34. How do I obtain an interaction in SPSS to describe how a fixed covariate influences a repeated measures interaction?

  35. What is the difference between within subjects effects and within subjects contrasts in SPSS?

  36. What summary measures can I use to describe repeated measures?

  37. How do I test for a trend, or contrast, between group means in a one-way ANOVA representing different subjects and also check location of asymptotes on a curve?

  38. How do I interpret subsets in Tukey's HSD output?

  39. How do I compare all pairwise comparisons in a between subjects anova (and in a repeated measures anova)?

  40. Why won't SPSS let me do post hoc tests involving a within-subjects factor?

  41. How do I do a simple effects analysis in SPSS?

  42. How do I adjust p-values for number of comparisons using SPSS, R or in a spreadsheet?

  43. Adjusted p-values

  44. Repeated measures, Mixed models and Split-plot designs: A Rant

  45. How do I check Normality assumptions in repeated measures analyses in SPSS?

  46. What is the formula for Mauchly's W used for testing sphericity in univariate repeated measures anova?

  47. Fitting linear orthogonal polynomials

  48. How do I compare group means in a non-standard post-hoc contrast?

  49. How do I compare a set of group means with a control group mean?

  50. How do I manually compute t-statistics to compare means in a repeated measures ANOVA having 3 or more groups?

  51. Formulae for interaction sums of squares in balanced designs