In: Statistics and Probability
The average price for new mobile homes is known to be distributed with population standard deviation of 300. If a random sample of 36 homes resulted in a sample mean of 55, 000, obtain a 90% confidence interval.
Solution :
Given that,
Point estimate = sample mean =
= 55000
Population standard deviation =
= 300
Sample size = n = 36
At 90% confidence level
= 1-0.90% =1-0.90 =0.10
/2
=0.10/ 2= 0.05
Z/2
= Z0.05 = 1.645
Z/2
= 1.645
Margin of error = E = Z/2
* (
/n)
= 1.645* ( 300 / 36
)
= 82.24
At 90 % confidence interval estimate of the population mean is,
- E <
<
+ E
55000 - 82.24 <
< 55000 + 82.24
54917.76 <
< 55082.24
( 54917.76 ,55082.24 )