In: Statistics and Probability
In order to estimate the Mean weight of carry-on luggage, an airline selected and weighed, a random sample of 25 pieces of carry-on luggage. The sample mean was 32 pounds with a sample standard deviation of 9 pounds. Compute and explain a 90% confidence interval estimate of the population mean weight of all carry-on luggage.
Given that,
= 32
s =9
n = 25
Degrees of freedom = df = n - 1 = 25- 1 = 24
At 90% confidence level the t is ,
= 1 - 90% = 1 - 0.90 = 0.1
/ 2 = 0.1 / 2 = 0.05
t
/2,df = t0.05,24 = 1.711 ( using student t
table)
Margin of error = E = t/2,df
* (s /
n)
= 1.711* ( 9/
25) = 3.1878
The 90% confidence interval estimate of the population mean is,
- E <
<
+ E
32 - 3.1878 <
< 32+ 3.1878
28.8122 <
< 35.1878
(28.8122,35.1878 )