Question

Construct an 80% confidence interval to estimate the population mean using the data below. x = 19 s-4.3 n=21 What assumptions need to be made about this population? The 80% confidence interval for the population mean is from a lower limit of an upper limit of

Answer 1

solution:-
given that x = 19 , = 4. , n = 21
80% confidence for df = 21-1 = 20 is t = 1.325
confidence interval formula
=> x +/- t * s/sqrt(n)
=> 19 +/- 1.325 * 4.3/sqrt(21)
=> 17.7567 , 20.2433
lower limit = 17.7567
upper limit = 20.2433  

(rounded 4 digits)

--------------------------------------------------

solution:-
given that mean = 2.64 , standard deviation = 0.0898
90% confidence with df = 14 is t = 1.761
confidence interval formula
=> x +/- t * s/sqrt(n)
=> 2.64 +/- 1.761 * 0.0898 /sqrt(15)
=> 2.60 , 2.68