An article claims that 12% of trees are infested by a bark beetle. A random sample of 1,000 trees were tested for traces of the infestation and found that 127 trees were affected. what is the value of the z-test statistic?

The value of the z-test statistic is

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:

At the alternative hypothesis, we test if the proportion is different of 12%, that is:

The test statistic is:

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

0.12 is tested at the null hypothesis:

This means that

A random sample of 1,000 trees were tested for traces of the infestation and found that 127 trees were affected.

This means that

What is the value of the z-test statistic?

The value of the z-test statistic is