Find the critical value $z_{\alpha / 2}$ that corresponds to the given confidence leve $99 \%$ $z_{\alpha / 2}=$ (Round to two decimal places as needed.)

Step 1 ：The critical value $z_{\alpha / 2}$ corresponds to the z-score that cuts off the upper $\alpha / 2$ area in the tail of the standard normal distribution.

Step 2 ：In this case, we are given a confidence level of $99 \%$, which means $\alpha = 1 - 0.99 = 0.01$.

Step 3 ：Therefore, we need to find the z-score that cuts off the upper $0.01 / 2 = 0.005$ area in the tail of the standard normal distribution.

Step 4 ：We can use the inverse of the cumulative distribution function (CDF) to find this z-score.

Step 5 ：We need to input $1 - 0.005 = 0.995$ into the inverse CDF function to find the z-score that cuts off the upper $0.005$ area in the tail of the standard normal distribution.

Step 6 ：The critical value $z_{\alpha / 2}$ that corresponds to the given confidence level $99 \%$ is \(\boxed{2.58}\).