A random sample of 63 SAT scores of students applying for me

A random sample of 63 SAT scores of students applying for merit scholarships showed an average of 1400 with a standard deviation of 240.

If we want to provide a 95% confidence interval for the SAT scores, the degrees of freedom for reading the critical values of

Solution

Here the population mean and standard deviations are not known. Both needs to be estimated. Due to estimation the population variance degrees of freedom reduces by 1 than the total sample size. Hence the appropriate answer is 63-1=62