Question

The Museum of Science in Boston has an exhibit in which metal balls drop down a chute, bounce around, and wind up in one of 21 bins. After 1000 balls have dropped, the heights within the bins clearly follow a bell-shaped curve. The standard deviation is 3 bins.

About how many balls are in bins 1 through 17?

A) 500
B) 680
C) 950
D) 975

Answer 1

0.09121×1000=91

if you have 21 bins then the 'middle bin' is bin 11 (starting at 1)

So the 'mean' of this distribution is 11.

Therefore from 1000 balls the number of balls is 0.91 x 1000.

So therefore the answer would be C