An experiment was conducted to study the effect of four drugs on blood pressure. The results are given in the following table
Drugs n x s
1 .10 121 10.2
2 .10 115 11.5
3 .7 118 12
4 .6 125 11.8
(a) Construct a 95% condence interval for the dierence between the average blood pressure of patients in groups 1 and 3.
(b) Determine if there is a signicance dierence between the effect of any two of the drugs. (Use alpha= :01)