The mean life of a particular brand of light bulb is 1000 hours and the standard deviation is 50 hours.We can conclude that at least 75% of this brand of bulbs will last between ___.
A)900 and 1100 hours
B)950 and 1050 hours
C)850 and 1150 hours
D)800 and 1200 hours
E)1050 and 1250 hours

Question

Quizplus · Accepted Answer

According to Chebyshev's theorem, at least 75% of data lies within 2 standard deviations from the mean. Here, 2 standard deviations is 100 hours (2 * 50), so the range is 1000 ± 100, which is 900 to 1100 hours.

The Mean Life of a Particular Brand of Light Bulb