A company with a fleet of 150 cars found that the emission systems of 7 out of 22 they tested failed to meet pollution control guidelines. Is this strong evidence that more than 20% of the fleet might be out of compliance?
You are writing the null and alternative hypotheses. Should you use a left-tailed, right-tailed or two-tailed HA?
A) Left-tailed
B) Right-tailed
C) Two-tailed
D) Does not make any difference
E) Unable to determine with the given information
Two-tailed?
It is right-tailed
Answer B
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To determine whether the evidence suggests that more than 20% of the fleet might be out of compliance, we need to set up null and alternative hypotheses and conduct a hypothesis test.
Null hypothesis (H0): The proportion of cars out of compliance in the fleet is equal to or less than 20% (p ≤ 0.20).
Alternative hypothesis (HA): The proportion of cars out of compliance in the fleet is greater than 20% (p > 0.20).
Now, to choose the type of hypothesis test we need to consider the nature of the alternative hypothesis. In this case, we are specifically interested in determining if the proportion of cars out of compliance is greater than 20%, which makes it a right-tailed hypothesis test (B) because we are looking at the right tail of the distribution.
Therefore, the correct answer is B) Right-tailed.