# Thread: Standard Deviation. No idea!

1. Originally Posted by sam93
Post four part 1?

Are you reffering to question four? I am slightly confused??
Yes.

2. I did this, using just the freq. (i guess i ignore the times) i wrote it out, and used the calculator. The answers were wrong.

These are the correct ones (according to the sheet):
Mean - 32
S.D -10.7

Mean - 32.1
S.D. - 10.5

? Super Confused!!

3. How are you getting a mean of 32 for question 4, part 1?

Frequencies are 1,3,6,16,2,2

4. I didn't get that: mine was 5.

But when you enter in the info, click "mark now" it marks it and then gives the correct answer. The one in my previous post was what it had as the correct answer?

5. Originally Posted by sam93
I didn't get that: mine was 5.

But when you enter in the info, click "mark now" it marks it and then gives the correct answer. The one in my previous post was what it had as the correct answer?
Ok, good.

That's odd that it had the answer as 25. Hmmm. I get 5 as well for mean, and 5.164 for standard deviation.

6. ..maybe this is why I am confused?

I often wonder wether they put the correct answer on them, or if [I]they[I]have mad a mistake. Probably not, but the question should be explained better I feel

7. Originally Posted by sam93
..maybe this is why I am confused?

I often wonder wether they put the correct answer on them, or if [I]they[I]have mad a mistake. Probably not, but the question should be explained better I feel
How about the swimming question before that? It has a frequency involved, did you match that answer? If so, then their answer for question 4 might be incorrect.

8. Nevermind, I got it. I misread your question. You want frequency means and standard deviations. That works like this:

Multiply each time interval, the maximum one, by the frequency. You should get:

45
150
560
90
110

This adds up to 960. Now, the total frequency is 30, so mean is 32.
32

9. No, I guessed that had something to do with the lenghts. Because when you put in the answer it has _______lengths. I havn't done that yet.

The problem is, I have to get over 70%. I must keep trying until I do. Every time I re-do the test, the data changes, and it becomes hard to work out whast I could be doing wrong.

10. I understand! Will this be the same on the swimming one, multiply by the highest value (I always thought it was the M.P, maybe where I am going wrong)

11. Yes, it should be the same.

I'll have to build another lesson that accounts for frequencies.

12. Thanks for all of your help.

I'll do it again and see if i get over 70%

Thanks again

13. Originally Posted by sam93
Thanks for all of your help.

I'll do it again and see if i get over 70%