If light bulbs have lives that are normally distributed with a mean of 2500 hours and a standard deviation of 500 hours, approximately what percentage of light bulbs has a life of more than 3000 hours?

Question

Quizplus · Accepted Answer

A life of 3000 hours is 1 standard deviation above the mean (2500 + 500). In a normal distribution, approximately 68% of the data falls within 1 standard deviation of the mean, leaving 32% outside this range. Since the distribution is symmetric, about 16% of the data is more than 1 standard deviation above the mean.

If Light Bulbs Have Lives That Are Normally Distributed with a Mean