Question

The mean of a set of $20$ observation is $19.3$ . The mean is reduced by $0.5$ when a new observation is added to the set. The new observation is

• A. $19.8$
• B. $8.8$
• C. $9.5$
• D. $30.8$

Answer 1

Answer: (B)

$8.8$

Sum of all numbers $=19.3\times 20=386$
New mean $=19.3-0.5=18.8$
New sum $=21\times 18.8=394.8$
Thus new number added $=394.8-386=8.8$