Question

A certain type of storage battery lasts, on average, 3.2 years with a standard deviation of 0.44 year. Assuming that battery life is normally distributed, find the probability that a given battery will last less than 2.5 years.

Answer 1

$$P(X<2.5)=P(Z<\dfrac{2.5-3.2}{0.44})$$

$$\approx P(Z<-1.590909)\approx0.055815$$