A purchasing manager at a university is investigating which brand of LCD projector to purchase to equip "smart" classrooms. Of interest to her is the variability of the lifetime of the light bulbs used in the projectors. One company has published the following information regarding the lifetimes of a sample of20

bulbs used in its LCD projectors:

10

5

0

Frequency

2

6

10

2

700750800850900

Bulb lifetime (in hours)

Based on this histogram, estimate thestandard deviationof thesampleof

20

lifetimes.Carry your intermediate computations to at least four decimal places, androundyour answer to at least one decimal place.