The mean and S.D. of sample of size 10 were found to be 9.5 and 2.5 respectively. Later on an additional observation became available. This was 15 and was included in the original sample. Find the mean and S.D. of the 11 observations.

The mean and S.D. of a sample of size 10 were found to be 9.0 and 2.0 respectively. Later on, an additional observation 25 was included in the original sample. Find the mean and S.D. of the final 11 observations.

The mean and S.D. of a group of 100 observations were found to be 20 and 3 respectively. Later on its was found that three observations were incorrect which were recorded as 21,21 and 18 find the mean S.D. if the incorrect observations were omitted.

The means of two samples of size 40 and 50 were found to be 54 and 63 respectively. Their standard deviations were 6 and 9 respectively. The variance of the combined sample of size 90 is

The mean of two samples of sizes 200 and 300 were found to be 25, 10 respectively. Their standard deviations were 3 and 4 respectively. The variance of combined sample of size 500 is

For a group of 200 students the mean and S.D. of marks obtained by them were found to be 40 and 15 respectively. Later on, it was found that the score 23 was misread as 32. Find the correct mean and correct S.D.

The mean of two samples of sizes 200 and 300 were found to be 25,10 respectively.Their standard deviations were 3 and 4 respectively.The variance of combined sample of size 500 is