Answer :
Answer:
The value of the z-test statistic is [tex]z = 0.68[/tex]
Step-by-step explanation:
An article claims that 12% of trees are infested by a bark beetle.
At the null hypothesis, we test if the proportion is of 12%, that is:
[tex]H_0: p = 0.12[/tex]
At the alternative hypothesis, we test if the proportion is different of 12%, that is:
[tex]H_1: p \neq 0.12[/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.
0.12 is tested at the null hypothesis:
This means that [tex]\mu = 0.12, \sigma = \sqrt{0.12*0.88}[/tex]
A random sample of 1,000 trees were tested for traces of the infestation and found that 127 trees were affected.
This means that [tex]n = 1000, X = \frac{127}{1000} = 0.127[/tex]
What is the value of the z-test statistic?
[tex]z = \frac{X - \mu}{\frac{\sigma}{\sqrt{n}}}[/tex]
[tex]z = \frac{0.127 - 0.12}{\frac{\sqrt{0.12*0.88}}{\sqrt{1000}}}[/tex]
[tex]z = 0.68[/tex]
The value of the z-test statistic is [tex]z = 0.68[/tex]