Critical Values

The critical value is a predefined z-score or t-score that is directly correlated to your confidence level (%). It is commonly represented as Z* or t*_df.

This means no calculations are necessary! They're pre-defined values based on our confidence level!

Scenario: Given a sample of 35 people with a sample mean of 23.2 and a population standard deviation of 3.2, find the critical value at a 95% confidence level.

Z^* = 1.960

Scenario: Given a sample of 35 people with a sample mean of 23.2 and a sample standard deviation of 3.2, find the critical value at a 95% confidence level.

df = n - 1
df = 35 - 1
df = 34

α = (1 - Confidence Level) / 2
α = (1 - 0.95) / 2
α = (0.05) / 2
α = 0.025

t*_df = 2.032