find critical z values, in each case assume normal distribution applies.

left tailed test. Alpha= 0.05

Can someone please explain how to do this?

Z = (score-mean)/SD

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability related to each Z score. Compare to .05.

To find the critical z-value for a left-tailed test with a given alpha level (significance level), you need to follow these steps:

Step 1: Determine the alpha level
In this case, the alpha level is given as 0.05. This means that the total area in the left tail (the rejection region) is 0.05, which also implies that the remaining area in the right tail is 1 - 0.05 = 0.95.

Step 2: Determine the critical z-value
Since we know the area in the right tail (0.95), we need to find the z-value corresponding to this area. This value is commonly referred to as the critical z-value.

To find the critical z-value, you can use a standard normal distribution table or a calculator. These resources provide the values of the cumulative distribution function (CDF) for different z-values. The CDF gives the probability that a standard normal random variable is less than or equal to a specific z-value.

In this case, we need to find the z-value that corresponds to an area of 0.95 in the right tail. Looking up the z-value in the standard normal distribution table or using a calculator, we find that the z-value corresponding to an area of 0.95 is approximately 1.645.

Therefore, the critical z-value for a left-tailed test with an alpha level of 0.05 is approximately -1.645.