Stat exam questions

T

tonycaldwell

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Dec 13, 2009
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Hello,

I have a few problems that I'm stuck on and could use some help please.

1. From a survey of likely voters, the 95% confidence interval for the proportion that would vote for the candidate was 44. 8 to 50.6. What was the margin of error?

2. If you estimate that the standard deviation of the cost of college textbooks is $20, how many must you check to be 95% confident that your sample mean will be within $4 of the population mean?

3. In 2006, a survey was taken of 24 statistics professors in southeastern community colleges to determine the number of pizzas that were brought to them by their students. The mean of the sample was 11.3 pizzas per semester with a standard deviation of 3.7. (Everyone knows the distribution of pizzas to stat professors is normal.) Develop a 95% confidence interval for the pizza mean.

Any help would be greatly appreciated.
 
tonycaldwell said:
Hello,

I have a few problems that I'm stuck on and could use some help please.

1. From a survey of likely voters, the 95% confidence interval for the proportion that would vote for the candidate was 44. 8 to 50.6. What was the margin of error?

2. If you estimate that the standard deviation of the cost of college textbooks is $20, how many must you check to be 95% confident that your sample mean will be within $4 of the population mean?

3. In 2006, a survey was taken of 24 statistics professors in southeastern community colleges to determine the number of pizzas that were brought to them by their students. The mean of the sample was 11.3 pizzas per semester with a standard deviation of 3.7. (Everyone knows the distribution of pizzas to stat professors is normal.) Develop a 95% confidence interval for the pizza mean.

Any help would be greatly appreciated.
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Please show us your work/thoughts, indicating exactly where you are stuck - so that we know where to begin to help you.
 
I don't even know where to start on these. I've complete the other 17 problems but I have no idea how to do these. I've looked back through my class notes but it looks lk emy professor didn't give detailed notes (or examples) for these types of problems. Any help that you can render will be great. Thanks for responding...
 
For problem #1 - first thing to do is to define margin of error:

Margin of error = Critical value x Standard deviation of the statistic

OR

Margin of error = Critical value x Standard error of the statistic

Next thing to would be to find the critical value of the given population......
 
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