Answer :
Answer:
We reject the null hypothesis and accept the alternate hypothesis, that is, that the mean is less than 13 ounces.
Step-by-step explanation:
The null hypothesis is:
[tex]H_{0}: \mu = 13[/tex]
The alternate hypotesis is:
[tex]H_{a}: \mu < 13[/tex]
The test statistic is:
[tex]z = \frac{X - \mu}{\frac{\sigma}{\sqrt{n}}}[/tex]
In which X is the sample mean, [tex]\mu[/tex] is the value tested at the null hypothesis, [tex]\sigma[/tex] is the standard deviation and n is the size of the sample.
13 is tested at the null hypothesis:
This means that [tex]\mu = 13[/tex]
N(µ,0.42)
This means that the standard deviation is 0.42, that is, [tex]\sigma = 0.42[/tex]
You collect a random sample of n = 35 boxes and find that the sample mean is 12.8.
This means that [tex]n = 35, X = 12.8[/tex]
Value of the test statistic:
[tex]z = \frac{X - \mu}{\frac{\sigma}{\sqrt{n}}}[/tex]
[tex]z = \frac{12.8 - 13}{\frac{0.42}{\sqrt{35}}}[/tex]
[tex]z = -2.82[/tex]
Pvalue of the test:
The pvalue of the test is the pvalue of z = -2.82.
Looking at the z table, z = -2.82 has a pvalue of 0.0024
0.0024 < 0.01, which means that we reject the null hypothesis and accept the alternate hypothesis, that is, that the mean is less than 13 ounces.