Gmat prep question

1. Find the Mean:

Add the Numbers given: 70, 75, 80, 85, 90, 105, 105, 130, 130, 130 = 1000
Mean = 1000 / 10 = 100.

2. Find 1SD below the mean.

100 - 22.4 = 77.6

3. Locate the numbers those are more than 1 SD below the mean.
(this is a tricky part, numbers have MORE than 1 SD below the MEAN means we have to find the numbers those are LESS than 77.6 .
The reason we find less is if we were asked to find the 2SD below mean then it would have been Mean - 2SD which would be 55.2 .
55.2 is More than 1SD below the mean because 55.2 is 2SD below the mean )

70 and 75 are less than 77.6

Thus IMO B

Mean= 100

One std dev below the mean = 100 - 22.4 = 77.6

Ans : 2

Thanks Shovan,

If we are asked to find 2SD below mean, than also we would find numbers < (Mean - 2SD)?

Yes, B is the correct answer.

If we are asked to find 2SD below mean, than also we would find numbers < (Mean - 2SD)?

You're right.