Determine whether the hypothesis test is left-tailed, right-tailed, or two-tailed.
\[
\begin{array}{l}
H_{0}: \sigma^{2}=138 \\
H_{a}: \sigma^{2} \neq 138
\end{array}
\]
What type of test is being conducted in this problem?
A. Two-tailed test
B. Right-tailed test
C. Left-tailed test
Answer
Final Answer: \(\boxed{\text{A. Two-tailed test}}\)
Step 1 ：Determine the type of test by looking at the alternative hypothesis (H_a).
Step 2 ：If H_a is testing for a value greater than the null hypothesis, it's a right-tailed test.
Step 3 ：If H_a is testing for a value less than the null hypothesis, it's a left-tailed test.
Step 4 ：If H_a is testing for a value different from the null hypothesis (either greater or less), it's a two-tailed test.
Step 5 ：In this case, H_a is testing for a value different from the null hypothesis, so it's a two-tailed test.
Step 6 ：Final Answer: \(\boxed{\text{A. Two-tailed test}}\)
