Suppose the number of defects in asweater from a population of sweaters produced from a textile factoryare normally distributed with an unknown population mean and a population standard deviation of0.06

defects. A random sample of sweatersfrom the population produces a sample mean ofx

=1.3

defects.

What value ofz

should be used to calculate a confidence interval with a95%

confidence level?

z

0.10

z

0.05

z

0.025

z

0.01

z

0.005

1.282

1.645

1.960

2.326

2.576