An exercise taken from Ott and Longnecker (#15.12) involves
the measurement of time that commercials are able to hold
children's attention.  The two experimental factors under
study are

Factor A: Age group  (A1: 5-6 yrs, A2: 7-8 yrs, A3: 9-10 yrs)
Factor B: type of product (B1: breakfast cereals, B2: video games)

Use the two-way ANOVA applet to obtain the sums of squares for 
main effects of factor A
main effects of factor B
interaction effects of factors A and B.

The treatment means for attention spans by age and product type are

A1B1: 22.8
A1B2: 23.2
A2B1: 19.5
A2B2: 30.6
A3B1: 22.0
A3B2: 45.6

Be sure to choose n=10 observations per treatment combination.

Specify the largets MSE available.  (MSE=50)

Imagine that these exact same treatments and variances had been obtained
from an experiment half the size (n=5 observations per treatment
combination).  Would the pvalues for treatment effects be bigger or
smaller?  Try it and see.