Question

The mean of 5 observations is 50. One of the observations was removed from the data, hence the mean became 45. Find the observation which was removed.

Answer 1

We have,

The mean of 5 observations is 50.

⇒ The total sum of 5 observations = 50 × 5 = 250

Also, the mean of 4 observations is 45.

⇒ The total sum of 4 observations = 45 × 4 = 180

So, the observation which was removed = 250 − 180 = 70.