Confidence Interval Steps

Saturday, 17 August 2019

8:52 PM

1. Figure out the confidence level -
2. Find
3. If the variance is known, find  (given to you as we don't use standard tables)
4. Interval is

 

 

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If variance is not known (usually the case),

 can be approximated to

We can use  in place of our variance

Instead of  , we use

 

Use t-confidence interval when  is a random variable, rather than a calculated variable

 

 

When the sample size is large  we can apply the Central Limit Theory and use -scores