The life expectancy of a typical lightbulb is normally distributed with a mean of 4,000 hours and a standard deviation of 42 hours. What is the probability that a lightbulb will last between 3,875 and 4,055 hours?
This is the concept of statistics, to solve the question we proceed as follows; We need to standardize our values; z(3,875)=(3,875-4000)/42 z(3,875)=-2.9762
z(4055)=(4055-4000)/42=1.3095=1.3
Therefore; p(3875<x<4055) =p(-3<z<1) =0.9034 The correct answer is D]
