Struggling with Statistics

Question

One sample has a mean of M=5 and a second sample has a mean of M=10. The two samples are combined into a single set of scores.

a. What is the mean for the combined set if both of the original samples have n=5 scores?

b. What is the mean for the combined set if the first sample has n=4 scores and the second sample has n=6?

c. What is the mean for the combined set if the first sample has n=6 scores and the second sample has n=4?

Answer 1

By definition of mean, each score in that sample can be equal to that sample's mean. So for each question, just multiply M*n for samples 1 and 2, add them together, and divide by the combined n = 10 scores. (n1+n2 happen to be the same for all 3 questions)

For question A:
M1*n1 = 5*5 = 25
M2*n2 = 10*5 = 50
Add together and divide by 10. The mean for question A is 7.5.

Try it with questions B and C and let me know how it goes!