Anyone know Statistics?

OK, I am in big trouble in my Elementary Statistics class and I need help. We have a chapter test tomorrow. Long story short I have a 101% average in the class, so I have been doing extremely well. We went out of town 3 weeks ago to Atlanta and I missed 1 class. In this one clas I missed an important lecture and nothing has made sense since. We didn't have class last week so I took that opportunity to get a lot of work done in my Anatomy class, but now, and yes the night before the test I realize I can not answer any questions on the practice exam at all I am going to fail this test tomorrow and lose my A average which is really going to hurt me. I am so upset with myself, I can't believe I let myself get behind. I was just struggling so hard with anatomy.

Here is the 1st question on the review:

A sociologist found that in a sample of 49 retired men, the average number of jobs they had during their lifetimes was 7.2. The standard deviation of the sample was 2.1. Construct a 90% confidence interval for the mean number of jobs a man had during his lifetime.

Then interpret your result.

Does anyone know how to work that, I have the formulas but just don't understand how to use them.

send me a message on AIM. I'll work you through it if you still need help. (mikenealis)

Give me just a few minutes I need to install AOL.. I haven't used it in forever.

Thank you. I still need help. I was just watching the lecture cd and it is making no sense to me.

Gosh, I hate statistics! I asked my super smart boyfriend though.

Andrew: she just needs to find the t value for 90% confidence when the df is 48
Andrew: df = N - 1
Andrew: N is 49 since there's 49 men in the sample
Andrew: so the df is 48
Andrew: then you look up 48 for 90% confidence on the t-value table
Andrew: or the closest number
Andrew: which will probably be 40
Andrew: and that number is t
Andrew: then its Sample Mean - t x sample standard deviation
Andrew: for the lower limit
Andrew: and Sample Mean + t x sample standard deviation
Andrew: for the upper limit
Andrew: then it's 7.2 - t x 2.1 for the lower limit
Andrew: 7.2 +t x 2.1 for the upper limit
Andrew: then the results will be "90% of men have between LL and UL jobs in their lives"
Andrew:
LL = 3.66
UL = 10.7

"90% of men have between 3.66 and 10.7 jobs in their lives"

I hope that helps and makes more sense to you than it does to me!

Wow, you're having such a tough semester, Tanya!

Originally Posted by squirtle

Give me just a few minutes I need to install AOL.. I haven't used it in forever.

Thank you. I still need help. I was just watching the lecture cd and it is making no sense to me.

Click to expand...

Or you can just look at the post above. Saves the install. I just suggested the AIM because you have the little running guy icon thing by your name.

Originally Posted by katie27

Gosh, I hate statistics! I asked my super smart boyfriend though.

Andrew: she just needs to find the t value for 90% confidence when the df is 48
Andrew: df = N - 1
Andrew: N is 49 since there's 49 men in the sample
Andrew: so the df is 48
Andrew: then you look up 48 for 90% confidence on the t-value table
Andrew: or the closest number
Andrew: which will probably be 40
Andrew: and that number is t
Andrew: then its Sample Mean - t x sample standard deviation
Andrew: for the lower limit
Andrew: and Sample Mean + t x sample standard deviation
Andrew: for the upper limit
Andrew: then it's 7.2 - t x 2.1 for the lower limit
Andrew: 7.2 +t x 2.1 for the upper limit
Andrew: then the results will be "90% of men have between LL and UL jobs in their lives"
Andrew:
LL = 3.66
UL = 10.7

"90% of men have between 3.66 and 10.7 jobs in their lives"

I hope that helps and makes more sense to you than it does to me!

Click to expand...

Hmmmm, that isn't the answer on the key. But some of that stuff looks familiar

The key says
6.707<u<7.694

I think, from what I just looked up, you only use the degrees of freedom, N-1 when the sample size is less than 30.