In: Statistics and Probability
Patsy Pennypincher is very concerned with the rising cost of education. She collected a sample of 20 institutions (n=20) and found a sample mean cost of $15,500 (mean = 15,500) and a sample standard deviation to be $3000 (s = 3000). Provide Patsy with a 98% confidence interval for this year’s tuition cost.
Please show your work.
Solution :
Given that,
= 15500
s = 3000
n = 20
Degrees of freedom = df = n - 1 = 20 - 1 = 19
At 98% confidence level the t is ,
= 1 - 98% = 1 - 0.98 = 0.02
/ 2 = 0.02 / 2 = 0.01
t /2,df = t0.01,19= 2.539
Margin of error = E = t/2,df * (s /n)
= 2.539 * (3000 / 20) = 1703.2130
The 98% confidence interval estimate of the population mean is,
- E < < + E
15500 - 1703.2130 < < 15500 + 1703.2130
13796.7870 < < 17203.2130
(13796.7870 , 17203.2130 )