Question

The expected (mean) life of a particular type of light bulb is 1000 hours with a standard deviation of 50 hours. The life of this world is normally distributed what is the probability that a randomly selected bulb would last fewer than 940 hours?

Answer 1

Answer:

11.5%

Step-by-step explanation:

To solve this problem, we can use the knowledge that there are z score tables that calculate probabilities based on z scores. Thus, we must calculate the z score.

The z score formula is $\frac{x- m}{s}$ , where x is the value, m is the mean, and s is the standard deviation. We can then plug our values in to get $\frac{940-1000}{50} = \frac{-60}{50} = -1.2$ as our z score. Plugging this into a table where table values represent the area to the left of the z score (as we want to calculate everything under 940), we get 0.115, or 11.5% as our answer