The mean life of a particular brand of light bulb is 1200 hours.If you know that at about 95% of this brand of bulbs will last between 1100 and 1300 hours, then what is the standard deviation of the light bulbs' life?
A)25
B)50
C)75
D)100
E)200

Question

Quizplus · Accepted Answer

The range from 1100 to 1300 hours represents approximately 95% of the data, which corresponds to 2 standard deviations in a normal distribution. Therefore, the total range of 200 hours (1300 - 1100) is equal to 4 standard deviations, making one standard deviation 50 hours.

The Mean Life of a Particular Brand of Light Bulb