Critical Values > T Critical Value
Not sure what I mean by a “critical value”? You might want to read this article first: What is a Critical Value?
What is a T Critical Value?
A T critical value is a “cut off point” on the t distribution. It’s almost identical to the Z critical value (which cuts off an area on the normal distribution); The only real difference is that the shape of the t distribution is a different shape than the normal distribution, which results in slightly different values for cut off points.You’ll use your t value in a hypothesis test to compare against a calculated t score. This helps you to decide if you should support or reject a null hypothesis.
How to Find a T Critical Value
You’ve got several options for finding a T value with technology, including:
- TI 83: See “How to Find t Critical Value on the TI 83.”
- Excel: See Excel T Test; Excel will calculate the T critical value as part of the process.
By hand
Step 1: Subtract one from your sample size. This is your df, or degrees of freedom. For example, if the sample size is 9, then your df is 8 – 1 = 7.
Step 2: Choose an alpha level. The alpha level is usually given to you in the question — the most common one is 5% (0.05).
Step 3: Choose either the one tailed T Distribution table or two tailed T Distribution table). This depends on if you’re running a one tailed test or two.
Step 4: Look up the df in the left hand side of the t-distribution table and the alpha level along the top row. Find the intersection of the row and column. For this example (7 df, α = .05,) the t crit value is 1.895.
Need help with a homework or test question? With Chegg Study, you can get step-by-step solutions to your questions from an expert in the field. Your first 30 minutes with a Chegg tutor is free!
Statistical concepts explained visually - Includes many concepts such as sample size, hypothesis tests, or logistic regression, explained by Stephanie Glen, founder of StatisticsHowTo.
Comments? Need to post a correction? Please post a comment on our Facebook page.