Z-test. How to find critical value for one tail test?
YOU determine the critical value by what level of alpha error… P = .05 or .01 or .001.
Then you see how the probability of the Z score on the Z table relates to your chosen level.
So, if the alpha level is .05 and the sample is 10, the critical value would be 1.833??
To find the critical value for a one-tail z-test, you need to follow these steps:
1. Determine the significance level (α) for your test. This is the predetermined level at which you will reject the null hypothesis. The most common significance levels are 0.05 (5%) and 0.01 (1%).
2. Identify the tail direction of your test. In a one-tail test, you are specifically testing if the sample mean is significantly greater than or less than the population mean.
3. Look up the critical value in the standard normal distribution table (also known as the Z-table). The critical value will correspond to the given significance level and tail direction.
4. If your test is one-tailed to the right, look up the value for 1 - α in the standard normal distribution table. If your test is one-tailed to the left, directly look up the value for α in the table.
5. Once you have located the appropriate value in the Z-table, multiply it by -1 if your test is one-tailed to the left. This is because the critical value for the left tail is negative, while the right tail is positive.
6. The resulting value is the critical value for your one-tail test.
Note that another option to obtain the critical value is to use statistical software or calculators that can provide critical values based on the specified significance level and tail direction.