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To calculate critical values in Google Sheets, one can use the TDIST function to calculate the student’s t-distribution percentiles for the given degrees of freedom and confidence level. The critical value for a given confidence level can then be calculated by inputting the confidence level value into the TDIST function. The result of the function is the critical value that should be used for the given confidence level.
Whenever you perform a , you will get a test statistic as a result. To determine if the results of the test are statistically significant, you can compare the test statistic to a critical value.
If the absolute value of the test statistic is greater than the critical value, then the results of the test are statistically significant.
To find a t-critical value in Google Sheets, you can use the following syntax:
- T.INV(probability, deg_freedom) – Returns t-critical value for a one-tailed t-test.
- T.INV.2T(probability, deg_freedom) – Returns t-critical value for a two-tailed t-test.
To find a z-critical value in Google sheets, you can use the following syntax:
- NORM.S.INV(probability) – Returns critical value for a one-tailed z-test.
- NORM.S.INV(probability/2) – Returns critical value for a two-tailed z-test.
The following examples show how to use each of these functions in practice.
Example 1: One-Tailed T-Test Critical Value
To find the t-critical value for a left-tailed test with a significance level of 0.05 and degrees of freedom = 11, we can type the following formula into Google Sheets:
The critical value is -1.79588.
Example 2: Two-Tailed T-Test Critical Value
To find the t-critical value for a two-tailed test with a significance level of 0.05 and degrees of freedom = 11, we can type the following formula into Google Sheets:
The critical value is 2.200985.
Example 3: One-Tailed Z-Test Critical Value
To find the z-critical value for a left-tailed test with a significance level of 0.05, we can type the following formula into Google Sheets:
The critical value is -1.64485.
Example 4: Two-Tailed Z-Test Critical Value
To find the z-critical value for a two-tailed test with a significance level of 0.05, we can type the following formula into Google Sheets:
The critical value is -1.96.
Cautions on Finding Critical Values in Google Sheets
Note that the T.INV(), T.INV.2T(), and NORM.S.INV() functions will throw an error if any of the following occur:
- If any argument is non-numeric.
- If the value for probability is less than zero or greater than 1.
- If the value for deg_freedom is less than 1.