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Press ‚Ù—@@@OK@@@   to access the confidence interval feature in the 
calculator.   Press ˜˜˜@@@OK@@@ to select option 4. Z-INT: p1 – p2..   
Enter the following values: 
 
 
 
When done, press @@@OK@@@.  The results, as text and graph, are shown below: 
 
   
 
Example 5
 – Determine a 95% confidence interval for the mean of the 
population if a sample of 50 elements has a mean of 15.5 and a standard 
deviation of 5.  The population’s standard deviation is unknown. 
 
Press ‚Ù—@@@OK@@@   to access the confidence interval feature in the 
calculator.   Press — — @@@OK@@@ to select option 5. T-INT: µ.   Enter the 
following values: 
 
 
When done, press @@@OK@@@.  The results, as text and graph, are shown below: