Probability that a washer is defective

$\begin{array}{l}=1-\mathrm{Probability}\mathrm{that}\mathrm{a}\mathrm{washer}\mathrm{is}\mathrm{not}\mathrm{defective}\hfill \\ =1-0.7698\hfill \\ =0.2302\hfill \end{array}$

Therefore the percentage of defective washers=23.02.

* Example 4.93*: The mean of a normal distribution is 60 and 6% of the values are greater than 70. Find the SD of the distribution?

* Solution*: Let

We have $P(X>70)=\frac{6}{100}=0.6$ (given)

Therefore

$P\left(\frac{x-\mu}{\sigma}>\frac{70-\mu}{\sigma}\right)=0.6$

i.e.,

$P\left(Z>\frac{70-60}{\sigma}\right)=0.6$

or

$P\left(Z>\frac{10}{\sigma}\right)=0.6$

Let ${Z}_{1}=10/$

Start Free Trial

No credit card required