Question

The mean of 25 observations is 80 and the mean of another 55 observations is 60. Determine
the mean of whole sets of observations.​

Answer 1

Step-by-step explanation:

Let the observations are x1,x2,x3,......x80.

According to question,

(x1+x2+x3+.....+x25) ÷ 25 = 80

(x1+x2+x3+.....+x25) = 80×25 = 200

and

(x26+x27+.......+x80) ÷ 55 = 60

(x26+x27+.......+x80) = 60×55 = 3300

Now, the mean of whole sets of observations is

(x1+x2+x3+............+x79+x80) ÷ 80

= ( 200 + 3300 ) ÷ 80

= 3500 ÷ 80

= 43.75