Statistics Help

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rkivell

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Dec 12, 2005
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Advanced Statistics

The following 5 questions are giving me a hard time. We got our homework back today and these are the ones I missed. Can someone please show me how to work these problems?

1. Suppose the sample size n=50 and sample proportion p= .6 Find the 95% margin of error when estimating true proportion.
2. Distribution of weights of fish has mean 1 lb. and standard deviation of .3 pounds. A random sample of 36 fish. Find the probability sample average weight mean of x will be more than 1.1 lbs.
3. A TV pollster believes 70% of all TV households would tune in. Random sample of 500 TVs. 365 indicated they were tuned in.
a. Find 99% confidence interval for true proportion of TV households tuned in
b. Based on interval in a) can you reject the pollster’s claim?
4.The unemployment rate is 6%. There is a sample of 700 people. What is the probability p is at most 5%?

This one gave me the most difficulty as I missed all 5 points on the problem.

An experiment compares diets A&B over a 30 day period. The sample mean of Diet A is 23.5 and the sample mean of Diet B is 15.6. The standard deviation of Diet A is 2.45 and s.d. of Diet B is 1.75. The sample size is 50 for Diet A and 50 for Diet B.

Find the 95% confidence interval for true difference in mean weight loss for the 2 diets.
Based on this, is there a difference in mean weight loss?
 
No, please provide what you attempted first, and then we will let you know where you went wrong.
 
?

I don't know exactly what you want me to write down. I barely attempted them BECAUSE I did not know how to do them. I got 1/5 each on the first 4 for basically recopying the numbers from the problem down. I did not even attempt the 5th because I didn't know where to start. That is why I am asking how to do them. I don't even need an answer. Could someone please just show me how to work the problems. Thanks.
 
Just show them to you? How will you learn that way? You really have no idea?
 
Basically, if I see the steps, then I can work through them to find the solution. After seeing how to do it, I could repractice it to review it for our next test. And no I really don't have a clue how to do them. That's why I missed them even with text and online CD help. The last 2 chapters of this class have been increasing in difficult compared to previous chapters.
 
What are you talking about? If you read that topic you'd see that I apologized for starting a new topic instead of replying. Thanks though.
 
No! By posting the same question on another site, it usually means that you just want answers, or else you would have waited for help on this site. Personally, I feel this is some kind of exam that you want us to do for you.
 
Reply

Sorry, but I do not know exactly what I am struggling with. These were 5 problems out of a total of 50 that covered 3 chapters. Those are just the problems that I didn't know how to do.
 
Ok then, how about you post what steps you've taken so far or simply ask to help get started. We WILL NOT give you the answers. We can't help you if you don't help us figure out where you're having trouble, thanks!
 
G'day, Rkivell.

Don't worry; your questions are quite justified.

1. The "margin of error" is not a standard term but they may mean the bit you are adding and subtracting from the sample proportion to get the confidence interval for the true proportion. Apply the formula.

2. Remember that the distribution of sample means has the population mean as its mean. So this is actually just a normal distribution problem you will be familiar with: the mean is 1, the SD is 1, and we want to find P(X > 1.1). Do you see?

3. a) Plug'n'chug into the confidence interval for the true proportion formula.
b) What are your thoughts?

4. You would have done binomial distributions, and recall that the expected value, that is the mean, is given by np. Because np = 700 * 0.06 = 42, we can approximate with a normal distribution. A proportion at most of 5% is at most 0.5 * 700 = 35 people being unemployed. Look in your class notes for the binomial to normal approximation if you are unsure as to how to proceed.

5. Apply the confidence interval for the difference between two means formula. If zero is not included in the interval, there is evidence to suggest a difference.
 
jolly, if I was the boss of this board, you'd be barred quickly!

All you do is lurk in the background, and jump in when you see
a chance to pick on a poor new student; I have yet to see you
post anything helpful.

It is plain to see that this student is not looking for someone to
do his homework: he is stuck and needs help.

And I'd like to add that I feel better for this student after seeing
Unco's reply.

PLUS this student has NOT really been impolite; I see a few
"I'm sorry"'s from him...until he finally called jolly a jerk...
which was well deserved!
 
That's fine, Denis. I won't post anymore. I just felt a student who doesn't show any work and expects the tutor to pick up the slack, should not be helped. It has been bothering me for a while, but it felt good to finally let it out. Like I said, I'm done venting now.
 
Thanks

Thanks to Unco for your help. I will see what I can do with your help. Also thanks to Denis for support.
 
I'm sorry if I seemed rude. I did not mean to discourage you. I didn't realize that I might have been rude until after Denis said something. So, I'm sorry. I was only trying to help people help you out. I hope you can forgive me? :?
 
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