Find the value of zα/2 to construct a confidence interval with level:

a. 95%
b. 98%

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportions (.025 & .01, respectively) that relate to the Z scores.

95% interval = mean ± 1.96 SD, so Z = 1.96.

You do the second one.

I got it! the second one is Z = 2.326

Thanks!!! :)

To find the value of zα/2, we need to look up the critical value associated with the desired confidence level.

a. For a 95% confidence level, we need to find the value of zα/2. This means we want to find the z-value that represents the area under the standard normal distribution curve to the left of zα/2 equal to (1-α)/2 = 0.975.

To find this value, we can use a standard normal distribution table or a statistical software. Using a standard normal distribution table, we find that the critical value corresponding to a 0.975 cumulative probability is approximately 1.96. Therefore, zα/2 for a 95% confidence level is 1.96.

b. For a 98% confidence level, the process is the same. The desired z-value represents the area to the left of zα/2 equal to (1-α)/2 = 0.99. Using a standard normal distribution table, we find that the critical value corresponding to a 0.99 cumulative probability is approximately 2.33. Therefore, zα/2 for a 98% confidence level is 2.33.