How to Find the T Critical Value in Python?
To perform a T-test, we will get a test statistic as a result and determine whether the T-test results are statistically significant, we can compare the test statistic with the T critical value, if the absolute value of the test statistic is greater than the T critical value, then the test results are statistically significant.
T critical value can be found by using a T-distribution table or using statistical software. To find the T critical value, you need to specify the values:
- A critical level (q) (common values are 0.01, 0.05, and 0.10)
- The degrees of freedom (df)
Using these two values, you can find the T critical value to be compared with the test statistic.
Calculating T Critical Value using scipy.stats.t.ppf() function:
Determine the T critical value in Python, we can use the scipy.stats.t.ppf() function.
Syntax:
scipy.stats.t.ppf(q, df)
Parameters:
- q: The critical level to use.
- df: The degrees of freedom.
Right-Tailed Test
Let us consider that we want to find the T critical value of the right-tailed test when the critical level (q) of 0.10 and the degree of freedom (df) is 34.
Example:
Python3
# Import Library import scipy.stats # To find the T critical value scipy.stats.t.ppf(q = 1 - . 10 ,df = 34 ) |
Output:
The T critical value is 1.30695. When the test statistic is greater than this value, the results of the test are statistically significant or critical.
Left-Tailed Test
We consider that we want to find the T critical value of the left-tailed test when the critical level (q) of 0.10 and the degree of freedom (df) is 34.
Example:
Python3
# Import Library import scipy.stats # To find the T critical value scipy.stats.t.ppf(q = . 10 ,df = 34 ) |
Output:
The T critical value is -1.30695. When the test statistic is lesser than this value, the results of the test are statistically significant or critical.
Two-Tailed Test
We consider that we want to find the T critical value of two-tailed test when the critical level (q) of 0.10 and the degree of freedom (df) is 34.
Example:
Python3
# Import Library import scipy.stats # To find the T critical value scipy.stats.t.ppf(q = 1 - . 10 / 2 ,df = 34 ) |
Output:
When we perform a two-tailed test, there will be two critical values or in this case, the T critical values are 1.69092 and -1.69092.I f the test statistic is lesser than -1.69092 or greater than 1.69092 and the results of the test are statistically significant or critical.