question_answer

The mean and S.D. of 63 children on an arithmetic test are respectively 27.6 and 7.1. To them are added a new group of 26 who had less training and whose mean is 19.2 and S.D. 6.2. The values of the combined group as (i) the mean and (ii) the S.D. are

A)  25.1, 7.8    

B)  2.3,0. 8       

C)  1.5, 0.9           

D)  None of these