How to find critical Z scores for Confidence intervals 

 

*Z scores are only used for confidence intervals involving proportions and means when the population standard deviation is known*

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1. Identify the confidence level 

2. Subtract from 1 

3. Divide results by 2 

4. Use table to find score 

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Example: Find the Z score necessary to construct a 95% Confidence Interval 

1. Identify the confidence level 

   • 95%​

2. Subtract from 1 

   • 1 - 0.95 = 0.05

3. Divide results by 2 

   • 0.05 / 2 = 0.025​

4. Use table to find score 

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