Answer:
At 95% confidence level, she used 11 people to estimate the confidence interval
Step-by-step explanation:
The bounds of the confidence interval are: 740 to 920
Mean is calculated as the average of the lower and upper bounds of the confidence interval. So, for the given interval mean would be:
[tex]u=\frac{740+920}{2}=830[/tex]
Margin of error is calculated as half of the difference between the upper and lower bounds of the confidence interval. So, for given interval, Margin of Error would be:
[tex]E=\frac{920-740}{2}=90[/tex]
Another formula to calculate margin of error is:
[tex]E=z\frac{\sigma}{\sqrt{n}}[/tex]
Standard deviation is given to be 150. Value of z depends on the confidence level. Confidence Level is not mentioned in the question, but for the given scenario 95% level would be sufficient enough.
z value for this confidence level = 1.96
Using the values in above formula, we get:
[tex]90=1.96 \times \frac{150}{\sqrt{n} }\\\\ n = (\frac{1.96 \times 150}{90})^{2}\\\\ n=11[/tex]
So, at 95% confidence level her assistant used a sample of 11 people to determine the interval estimate
