Question

the mean of 10 observations is 7 and the mean of 15observations is 12. then find the mean of all observations

Answer 1

the mean of 10 observations is =7

so n = 10

sigma x i = 70

the mean of the 15 observations is 12

so n = 15

sigma x i = 180

so total n = 25

so total sigma is = 70+185 = 220

so total mean is = 220/25=8.8 is the mean of the total observation