6:38 For a group of 50 boys the mean score and the standard deviation of scores on a test are 59.5 and 8.38 For a group of 40 girls the same results are 54.0 and 8.23. Find the mean and S.D. of the combined group of 90 children. 6:38 For a group of 50 boys the mean score and the standard deviation of scores on a test are 59.5 and 8.38 For a group of 40 girls the same results are 54.0 and 8.23. Find the mean and S.D. of the combined group of 90 children