Question

The time (in minutes) required for six‑year old children to assemble a certain toy is believed to be normally distributed with a known standard deviation of 3.0. The data in Table B gives the assembly times for a random sample of 25 children.

8. What was the mean assembly time for this sample of 25 six‑year old children?

24.3792

9. What was the estimated standard deviation?

3.061977

  

10. What was the margin of error of the estimate for a 90% confidence interval?

11. What was the lower limit of the 90% confidence interval for average assembly time?

12. What was the upper limit of the 90% confidence interval for average assembly time?

Table B:

25.11
25.49
23.45
26
24.23
18.95
25.16
30.77
20.87
22.85
23.11
21.21
22.25
24.68
21.21
25.81
30.4
26.02
23.35
25.18
30.75
25.26
21.61
25.29
20.47

Hi, I need help with questions 10, 11 and 12. Is there a way I can do them on excel? Thanks!

Answer 1

As only question 10,11 and 12 are asked, I'll answer them by hand as well as excel.

interpretation :

The result shows that with 90% confidence, the average grade of students is 24.3792 plus or minus 1.010453%