Single Factor Analysis of Variance

blue population

_

x

1

18

s

1

1

purple population

_

x

2

20

s

2

1

green population

_

x

3

21

s

3

1

set

s

1

=

s

2

=

s

3

to:

0.75

1

1.25

reset

Means

SDs

shading

On

Off

Source	Sum of Squares	df	Mean Square	F Value	P Value
Between Groups	46.667	2	23.333	23.333	< .01
Within Groups	27.000	27	1.000
Total	73.667	29

This Demonstration shows how a single factor analysis of variance (ANOVA) works. There are three groups, each with sample size 10. You can change the mean or standard deviation of each group separately and observe the changes in the ANOVA table of results. The black line represents the grand mean and its value is at the top of the line. The significance of

F

is provided as

p<0.01

,

p<0.05

, or

p>0.05

based on a regular table for the distribution of

F

at 2 and 27 degrees of freedom.

You can set the standard deviations to be equal across the groups at 0.75, 1, and 1.25. The reset buttons set the means or standard deviations back to the default values. The shading buttons turn the shading of the curves on and off.