Constructing Confidence Intervals.In Exercises 17–26, construct the confidence intervals
Credit Rating: When consumers apply for credit, their credit is rated using FICO
(Fair, Isaac, and Company) scores. Credit ratings are given below for a sample of
applicants for car loans. Use the sample data to construct a 99% confidence interval
for the mean FICO score of all applicants for credit. If one bank requires a credit rating
of at least 620 for a car loan, does it appear that almost all applicants will have
suitable credit ratings?
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Question

Constructing Confidence Intervals.In Exercises 17–26, construct the confidence intervals
Credit Rating: When consumers apply for credit, their credit is rated using FICO
(Fair, Isaac, and Company) scores. Credit ratings are given below for a sample of
applicants for car loans. Use the sample data to construct a 99% confidence interval
for the mean FICO score of all applicants for credit. If one bank requires a credit rating
of at least 620 for a car loan, does it appear that almost all applicants will have
suitable credit ratings?
661 595 548 730 791 678 672 491 492 583 762 624 769 729

anonymous · Answer

I have the 
n=16
the mean is adding all numbers divided by 16= 660.3125
t- test distribution=2.947 
I don't know how to calculate S (since we don't know sigma) 
Please help!