Answer to Question #336412 in Statistics and Probability for Hee

Question

What is the probability that the shelf life of the

battery is between 500 and 550 days?

Answer 1

A certain type of battery has a mean shelf life of 600 days with a standard deviation of 28 days: $X\sim N(600,28^2).$

$$P(500<X<550)=P(Z<\dfrac{550-600}{28})$$

$$-P(Z\le\dfrac{500-600}{28})$$

$$\approx P(Z<-1.7857)-P(Z\le-3.5714)$$

$$\approx0.03707-0.00018$$

$$\approx0.0369$$