8 5 Consider an experiment designed to compare four treatment means 2 3 and M4 using sample sizes of size n n n3 and n4 and sample variances s1 s3 s3 and s a Suppose the sample sizes are the same n n n3 n4 Show that sy is the average of the four sample variances s s s s 4 b Does this hold if the sample sizes are not equal If not why not just use the average