## anonymous one year ago A lathe machine produces machine parts whose lengths are normally distributed with a standard deviation of 0.20 mm. A sample of 10 parts is found to have a mean of 16.35 mm. Based on this sample, what is the 95% confidence interval for the population mean ?

1. anonymous

@rational

2. rational

start by finding the "margin of error"

3. rational

whats the multipilier(Z*) value for 95% confidence interval ? (look up in ur notes)

4. anonymous

.95

5. rational

there will be a multiplier value, look up ur notes once

6. rational

For 95% confidence interval, the multiplier value is 1.96 : |dw:1432814569497:dw|

7. rational

therefore margin of error is $1.96*\frac{0.2}{\sqrt{10}} = ?$

8. anonymous

I feel like I messed up

9. rational

messed up what

10. anonymous

.0153664 is what I got and that does not seem right to me

11. rational

work it again use ur calculator

12. anonymous

calc says .1214314622

13. rational

looks good, round it to 0.12 maybe

14. rational

so the margin of error is 0.12

15. rational

subtract that from mean, what do u get ?

16. rational

16.35-0.12 = ?

17. anonymous

16.23

18. rational

yes thats the lower bound of confidence interval

19. rational

for upper bound simply add 16.35 + 0.12 = ?

20. anonymous

16.47

21. anonymous

16.22-16.47

22. rational

so the confidence interval is $\large (16.23,~ 16.47)$

23. anonymous

Tyty