Question

The mean of a set of 20 observations is 8 and of another set of 30 observations is 10. The mean of
combined set is
(1) 9.2
(2) 10.8
(3) 11.2
(4) 9.8

Answer 1

mean of combined set=(20×8+30×10)/(20+30),

=(160+300)/50,

=460/50,

=46/5=9.2