Question

The mean age from a sample of 41 employees at Stats R Us is 28, with a standard deviation of 6.9.

Construct a 94% confidence interval for the mean age for all Stats R Us employees.  

________ μ < μ___________

Construct a 96% confidence interval for the mean age for all Stats R Us employees.

________ μ < μ___________

Round all answers to two decimal places

Which of the following is correct?

• When we increase the confidence level, the margin of error decreases
• When we increase the confidence level, the margin of error increases also

Answer 1

Ans:

sample size,n=41

As,sample size is greater than 30,we can use normal distribution.

critical z value for 94% confidence level=1.88

94% confidence interval for the mean age

=28+/-1.88*(6.9/sqrt(41))

=28+/-2.03

=(25.97, 30.03)

critical z value for 96% confidence level=2.05

96% confidence interval for the mean age

=28+/-2.05*(6.9/sqrt(41))

=28+/-2.21

=(25.79, 30.21)

Correct option is:

When we increase the confidence level, the margin of error increases also.