Considering the situation described, we have that:
a) The critical value is of z = -1.645.
b) Since the test statistic is less than the critical value, we should reject the null hypothesis H0.
We have a left-tailed test, as we are testing if the proportion is less than a value. Hence the critical value is z with a p-value equals to the significance level, hence z with a p-value of 0.05, hence z = -1.645.
Considering the test statistic, for a left-tailed test, we have that:
In this problem, z = -2.39 is less than -1.645, hence we should reject the null hypothesis H0.
More can be learned about the test of an hypothesis at https://brainly.com/question/13873630
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