Using the Z table find the critical value for alpha 001 two

Using the Z table find the critical value for alpha= 0.01, two tailed test.

Solution

Find a Critical Value in Any Tail: Easy Steps

Main > Critical Values & Hypothesis Testing > Find a critical value

Critical values are used in hypothesis testing. The alpha level is the maximum probability where you reject the null hypothesis if the null hypothesis is true. The technique for looking up a critical value is very straightforward as long as you know if you have a left tailed test or right tailed test (or potentially, both).

Find a critical value for a confidence level

Sample question:Find a critical value for a 90% confidence level.

Step 1: Subtract the confidence level from 100% to find the level: 100% – 90% = 10%.

Step 2: Convert Step 1 to a decimal: 10% = 0.10.

Step 3: Divide Step 2 by 2 (this is called “/2”).
0.10 = 0.05. This is the area in each tail.

Step 4: Subtract Step 3 from 1 (because we want the area in the middle, not the area in the tail):
1 – 0.05 = .95.

Step 5: Look up the area from Step in the z-table. The area is 1.645. This is your critical value for a confidence level of 90%.

Common confidence levels and their critical values

You don’t have to perform the above calculations every time. This list of critical values and their associated two-tailed test confidence levels were calculated using the above steps:

Find a Critical Value: Two-Tailed Test

Sample question: Find the critical value for alpha of .01.

Step 1: Subtract alpha from 1.

1 – .01 = .99

Step 2 :Divide Step 1 by 2 (because we are looking for a two-tailed test).

.99 / 2 = .495

Step 3: Look at your z-table and locate the answer from Step 2 in the middle section of the z-table. The fastest way to do this is to use the find function of your browser (usually CTRL+F).

Z = 2.58