Question

A manufacturer of potato chips would like to know whether its bag filling machine works correctly at the 434 gram setting. It is believed that the machine is underfilling the bags. A 9 bag sample had a mean of 431 grams with a variance of 144. A level of significance of 0.01 will be used. Assume the population distribution is approximately normal. Is there sufficient evidence to support the claim that the bags are underfilled

Answer 1

Answer:

No, there is not sufficient evidence to support the claim that the bags are underfilled

Step-by-step explanation:

A manufacturer of potato chips would like to know whether its bag filling machine works correctly at the 434 gram setting.

This means that the null hypothesis is:

$H_{0}: \mu = 434$

It is believed that the machine is underfilling the bags.

This means that the alternate hypothesis is:

$H_{a}: \mu < 434$

The test statistic is:

$z = \frac{X - \mu}{\frac{\sigma}{\sqrt{n}}}$

In which X is the sample mean, $\mu$ is the value tested at the null hypothesis, $\sigma$ is the standard deviation and n is the size of the sample.

434 is tested at the null hypothesis:

This means that $\mu = 434$

A 9 bag sample had a mean of 431 grams with a variance of 144.

This means that $X = 431, n = 9, \sigma = \sqrt{144} = 12$

Value of the test-statistic:

$z = \frac{X - \mu}{\frac{\sigma}{\sqrt{n}}}$

$z = \frac{431 - 434}{\frac{12}{\sqrt{9}}}$

$z = -0.75$

P-value of the test:

The pvalue of the test is the pvalue of z = -0.75, which is 0.2266

0.2266 > 0.01, which means that there is not sufficient evidence to support the claim that the bags are underfilled.