Analysis of Variance (ANOVA)

1
Analysis of Variance (ANOVA)

• Post-Hoc Analysis

2
Word check

• When I talk about between groups variability,
  what am I talking about? What about within groups
  variability?
• What does SST represent? SSE? In general, how are
  these calculated?
• What does MS (either within or between)
  represent?
• What does the F ratio represent?

3
Regression and ANOVA

• http//www.stat.yale.edu/Courses/1997-98/101/anova
  reg.htm

4
Tukeys Method

• Compares the means for each pair of factor levels
  using a family error rate to control the rate of
  type I error.
• often called familywise error rate or
  experimentwise error rate
• The family error rate is the probability of
  making one or more type I errors for the entire
  set of comparisons.
• Tukey's method adjusts the individual confidence
  level, based on the family error rate you choose.

5
Multiple Comparisons

• These are confidence intervals
• Do the pairs of numbers capture 0?
• If so no significant difference in the means (we
  fail to reject the null hypothesis)
• If not, we can conclude that the mean for one
  expression exceeds the mean for the other