Question

A manufacturer of potato chips would like to know whether its bag filling machine works correctly at the 421 gram setting. It is believed that the machine is underfilling the bags. A 21 bag sample had a mean of 416 grams with a standard deviation of 29. A level of significance of 0.025 will be used. Assume the population distribution is approximately normal. Determine the decision rule for rejecting the null hypothesis. Round your answer to three decimal places.

Answer 1

Zstatistic < Zcritical ; then we reject the null

-0. 790 > - 1.96

Hence, we fail to reject the Null

Explanation:

Define the null and alternative hypothesis :

H0 : μ = 421

H1 : μ < 421

Given that :

Sample mean (x) = 416

Sample standard deviation, s = 29

α = 0.025

Sample size, n = 21

This is a lef tailed teast, hence if ;

Decision Rule :

Zstatistic < Zcritical ; then we reject the null

Zcritical at α = 0.025 (1 tailed) = - 1.96

Zstatistic = (x - μ) s/sqrt(n)

(416 - 421) / 29/sqrt(21)

Zstatistic = - 5 / 6.3283188

Zstatistic = - 5 / 6.3283188 = - 0.79

-0. 79 > - 1.96

Hence, we fail to reject the Null