Question

a certain type of battery has a mean shelf life of 600 days with a standard deviation of 28 days

Answer 1

Q:What is the probability that the shelf life of the battery is over 630 days?

Mean($\mu$ )= 600

Standard deviation($\sigma$ )= 28

Normal distribution formula$\Rightarrow z=\dfrac{\bar x-\mu}{\sigma}$

$\Rightarrow z=\dfrac{630-600}{28}$

$\Rightarrow z=1.071$

$P(z>1.071)= 0.5-0.3577=0.1423$