Using the TI-84 to Find Critical Values for Proportions

Steps to Find Critical Values

1. Go to 2nd VARS on your TI-84 calculator.
2. Choose Inverse Normal.

Inputs Required

• Level of Confidence: e.g., 90%, 95% etc.
• Mean: Keep at 0
• Standard Deviation: Keep at 1
• Option: Choose Center

Example Calculations

1. 90% Confidence Interval:
   • Enter 0.9 for level of confidence
   • Get critical value: Positive side is 1.645
2. 95% Confidence Interval:
   • Enter 0.95 for level of confidence
   • Get critical value: Positive side is 1.96

Important Notes

• Only care about the positive critical value.
• Values should match theoretical values found in statistical tables.