Laboratory tests show that the lives of light bulbs are normally distributed with
a mean of 750 hours and a standard
deviation of 75 hours. Find the
probability that a randomly selected
light bulb will last between 600 and 750
hours.

Given:

Laboratory tests show that the lives of light bulbs are normally distributed with a mean of 750 hours and a standard deviation of 75 hours.

To find:

The probability that a randomly selected light bulb will last between 600 and 750 hours.

Solution:

Let x be the lives (in hours) of light bulbs that are normally distributed.

We need to find the probability that a randomly selected light bulb will last between 600 and 750 hours, i.e., .

We have,

So,

Now,

Therefore, the required probability is 0.47725.

25% is the answer