The mean and variance of 7 observations are 8 and 16, respectively. If five of the observations are 2, 4, 10, 12, 14. Find the remaining two observations.
Let us assume the remaining two observations be x and y
The given observations in the question are 2, 4, 10, 12, 14, x, y
x + y = 14 (i)
It is also given in the question that,
Variance = 16
We know that,
x2 + y2 = 112 - 12
x2 + y2 = 100 (ii)
Thus, by using (i) we have:
x2 + y2 + 2xy = 196 (iii)
Now, from equation (ii) and (iii) we have:
2xy = 196 – 100
2xy = 96 (iv)
Now subtracting equation (iv) from (ii), we get:
x2 + y2 – 2xy = 100 – 96
(x – y)2 = 4
x – y = 2 (v)
Hence, from equation (i) and (v) we have:
When x – y = 2 then x = 8 and y = 6
And, when x – y = - 2 then x = 6 and y = 8
∴ The remaining observations are 6 and 8