## anonymous one year ago In a survey conducted with 600 participants across the United States, 450 were found to have studied science in college. If we were to predict the population proportion with a 99.7% confidence, what would the confidence interval be? 69.7% to 80.3% 73.23% to 76.76% 71.46% to 78.53% 73.5% to 76.5%

1. anonymous

I have the steps to this problem but I went wrong somewhere so I don't understand it

2. dan815

okay, so first 450/600 = ?

3. anonymous

0.75

4. dan815

okay now for a 99.7 %, u have to find the Z score for that

5. dan815

the next step is to find out what the standard deviation of thing should be

6. anonymous

ohhh see, that was the step I was missing, the standard deviation. Except idk how to do it

7. dan815

oh um also we know the center is definately 0.75 right

8. anonymous

yes..

9. dan815

or 75%, some of the choices u are given arent centered around that, so they can eliminated rightway

10. anonymous

would it be D?

11. dan815

nvm, all them are centered around 75% cant elimnate any argh

12. anonymous

oh okay so what do I do now

13. dan815

C is definitely wrong 71.46% to 78.53% as it should say 71.46% to 78.54%

14. anonymous

Well I wrote all the answers correctly so idk, I just checked

15. dan815

16. anonymous

So it's definitely not C?

17. dan815

What is the Z score u foundÉ

18. anonymous

the formula for z score is $z= \frac{ X-\mu }{ \sigma }$ right...

19. dan815

yes thats another one,. but we cant use that right now

20. anonymous

oh... then what do we use

21. dan815

i just mean we have to find Z score, for the 99.7 %

22. dan815

you have to look at that table and chart

23. anonymous

okay how do I do that

24. anonymous
25. anonymous

cause this is where I was stuck, I wasn't sure what numbers or whatever to look at on the chart

26. dan815

click on the 2 tail one

27. dan815

https://www.youtube.com/watch?v=_x6j-rH33Og you can watch this, i know it says typically not used for sample size greater than 30.. but the standard deviation is unknown so, what else can we do

28. anonymous

wait is it B?

29. dan815

no clue it looks like info is missing, what can we do with sample deviation is unknown and the pop deviation is unknown @hartnn

30. anonymous

here is the entire question

31. dan815

ya hm not sure

32. anonymous

ok I just need help cause I need to answer it soon

33. dan815

@ganeshie8 is the question missing info??

34. anonymous

so do you know anything..

35. anonymous

@ParthKohli

36. ganeshie8

I am eating at the moment but I found this https://answers.yahoo.com/question/index?qid=20140522184044AAlIk3W

37. anonymous

I'm on my school computer so yahoo is blocked, could you tell me what it says

38. ganeshie8

39. anonymous

no it's still blocked..

40. ganeshie8

try this

41. anonymous

thanks so much :)

42. ganeshie8

np