A research group asked 4488 Americans how they fall asleep, and 536 of them fall asleep on their stomach. Use the data to construct a 90% confidence interval for the percentage of all Americans who fall asleep on their stomach. Also find the margin of error. Round your answers to 3 decimal places.
A research group asked 4488 Americans how they fall asleep, and 536 of them fall asleep on their stomach. Use the data to construct a 90% confidence interval for the percentage of all Americans who fall asleep on their stomach. Also find the margin of error. Round your answers to 3 decimal places.
Obtain the 90% confidence interval for the percentage of all Americans who fall asleep on their stomach.
The 90% confidence interval for the percentage of all Americans who fall asleep on their stomach is obtained below as follows :
Use EXCEL Procedure for finding the critical value of z.
Follow the instruction to obtain the critical value of z:
- Open EXCEL
- Go to Formula bar.
- In formula bar enter the function as“=NORMINV”
- Enter the probability as 0.95
- Enter the mean as 0 and the Standard deviation as 1.
- Click enter
EXCEL output:
From the EXCEL output, the critical value of z at the 90% confidence level is 1.645.
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