The null and alternative hypotheses are given. Determine whether the hypothesis test is left-tailed, right-tailed, or two-tailed. What parameter is being tested?
\[
\begin{array}{l}
H_{0}: \sigma=4.2 \\
H_{1}: \sigma \neq 4.2
\end{array}
\]
Choose the correct answer below.
Two-tailed
Left-tailed
Right-tailed
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Step 1 ：The null hypothesis (H0) is a statement of no effect or no difference. The alternative hypothesis (H1) is a statement that there is an effect or a difference. In this case, the null hypothesis is that the standard deviation (σ) is equal to 4.2, and the alternative hypothesis is that the standard deviation is not equal to 4.2.

Step 2 ：The test is two-tailed because the alternative hypothesis does not specify a direction, it only states that the standard deviation is not equal to 4.2. This means that the test will consider both the possibility that the standard deviation is less than 4.2 and the possibility that it is greater than 4.2.

Step 3 ：The parameter being tested is the standard deviation (σ).

Step 4 ：Final Answer: The hypothesis test is \(\boxed{\text{Two-tailed}}\) and the parameter being tested is the \(\boxed{\text{standard deviation}}\).