The mean and standrad deviation of 100 items are 50, 5 and that of 150 items are 40, 6 respectively.
What is the combined standard deviation of all 250 items?

The mean and standrad deviation of 100 items are 50, 5 and that of 150 items are 40, 6 respectively. What is the combined mean of all 250 items?

The mean and standrad deviation of 100 items are 50, 5 and that of 150 items are 40, 6 respectively. What is the variance of all 250 items?

Mean and standard deviation of 100 items are 50 and 4 respectively. The sum of all squares of the items is

For a group of 100 observations, the arithmetic mean and standard deviation are 8 and sqrt(10.5) respectively. The mean and standard deviation of 50 items selected from these 100 observations are 10 and 2 respectively. Then the standard deviation of the remaining 50 observation is

The arithmetic mean and standard deviation of a set of 9 items are 43 and 5 respectively. If an item of value 63 is added to that set, then the new standard deviation of 10 item set given is