Question

If each item of the sample data or observation is decreased by 25, the Arithmetic mean will…​

Answer 1

Answer :-

Arithmetic mean of 12 observations is 15.

Thus, sum of 12 observations = 180.

After removing 25 and 20 from the series , Sum of 10 Observations :-

= 180 − 25 − 20 = 135.

Thus, mean = Sum/Number = 135/10 = 13.5.

Answer 2

Answer:

original mean - 25

Step-by-step explanation:

Let there are n terms, and mean be M

⇒ M = sum of n terms/n

⇒ Mn = sum of n terms

       As here are n terms, and 25 is decreased from each, total decrease = 25 + 25 + .. n times. = 25 * n = 25n

So,  new mean:

⇒ (sum of n term - 25n)/n

⇒ (Mn - 25n)/n

⇒ n(M - 25)/n

⇒ M - 25

         Mean is also decreased by 25.