Reducing Hostility

Step 1: Graphs
Graph > Boxplot > with Groups, Graph variable=Score, Categorical variable= Method

This uses alphabetic ordering. It is better to change to some other ordering, say by means.
Stat > Basic Statistics > Display Descriptive Statistics, Variable=Score, By variables= Method
shows the order by means to be B - A - C. Change the order by
Select column Method by clicking c2-T, Editor > Column > Value Order
Redraw boxplot to get left panel

Step 2: Summary Statistics
Stat > Basic Statistics > Display Descriptive Statistics, Variable=Score, By variables= Method

Groups n Mean Std

B 3 66.33 10.79

A 5 76.00 5.87

C 3 87.00 8.00

Groups	n	Mean	Std
B	3	66.33	10.79
A	5	76.00	5.87
C	3	87.00	8.00

Step 3: Hypothesis Test
Stat > ANOVA > Oneway, Response=Score, Factor=Method, Graphs > Residual vs. Fits Plot and Normal Plot
Change to Window Project Manager, select Graphs, Slect graphs you want, right-click, Choose Layout tool, Finish
both plots look ok, no problems with the assumptions

1) α=0.05
2) H₀: α₁ = α₂ = α₃=0 (no difference in the mean scores of the methods)
3) H_a: α_i≠0 for some i (some differences in the mean scores of the methods)
4) p-value=0.037 < α
5) We reject H₀, there are some differences in the mean scores of the methods

Step 4: Multiple Comparison
Stat > ANOVA > Oneway, Response=Score, Factor=Method, Comparisons > check Tukey

B A C

_________

_________

Interpretation: There is a stat. signif. difference between the mean scores of methods B and C. Other differences are not stat. signif., at least not at these sample sizes.