In: Statistics and Probability
Chapter 8. A sample of 36 patients in a doctor's office showed that they had to wait an average of 45 minutes with a standard deviation of 12 minutes before they could see the doctor.
Please provide a 95% confidence interval estimate for the average waiting time of all the patients who visit this doctor, and interpret your results (write a sentence explaining the results).
Solution :
Given that,
Point estimate = sample mean = =45
Population standard deviation =
= 12
Sample size n =36
At 95% confidence level the z is ,
= 1 - 95% = 1 - 0.95 = 0.05
/ 2 = 0.05 / 2 = 0.025
Z/2 = Z0.025 = 1.96 ( Using z table )
Margin of error = E = Z/2
* (
/n)
= 1.96 * ( 12 / 36 )
E= 3.92
At 95% confidence interval estimate of the population mean
is,
- E <
<
+ E
45 - 3.92 <
< 45+ 3.92
41.08 <
< 48.92
( 41.08 ,48.92 )