One sample has n 4 scores and M 10 A second sample has n

One sample has n = 4 scores and M = 10. A second sample has n = 8 scores and M = 4. If the two samples are combined, what is the mean for the combined sample?

a.

72/12 = 6

b.

14/5 = 2.8

c.

14/12 = 1.167

d.

Cannot be determined with the information given

Solution

Note that

Sum(x) = M * n

Thus, the sum of the first and second groups are

Sum1 = 10*4 = 40

Sum2 = 4*8 = 32

Thus, the grand sum is

Grand sum = 40 + 32 = 72

The total number of points is n1 + n2 = 4 + 8 = 12.

Thus, the mean of the combined sample is

grand mean = grand sum / grand sample size

= 72 / 12

= 6 [ANSWER, A]