A random sample of 64 students at a university showed an average age of 25 years

Question

A random sample of 64 students at a university showed an average age of 25 years and a sample standard deviation of 2 years. Of these 64 students, 20% are business majors. In order to develop a 98% confidence interval for the true average age of all students in the university, which one of the following is the right formula to use? x plusminus f_alpha/2 s/Squareroot n p plusminus z_alpha/2 Squareroot p(1 - p)/n x plusminus z_alpha/2 s/Squareroot n x plusminus z_alpha/2 sigma/Squareroot n The symbol for the variance of a sample of observations (of a quantitative variable) is:

Explanation / Answer

as we do not know the std deviation of the population ; we should use student t distribution

there fore 1st option is correct xbar +/talpha/2 *s/(n)1/2

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