URGENT:Confidence interval and hypothesis testing help.

Isamar

New member
Joined
Jul 16, 2013
Messages
1
Please show all the work and the methods used so that i may learn the step by step process and understand. Thank you


1.In a SRS of 30 subway cars during rush hour, the average number of riders per car was 82.5 with a standard deviation of 4.7 (assume the sample data was approximately normal). Establish and interpret a 90% confidence interval for the average number of riders per car during rush hour.



2.A building inspector inspects 245 homes and finds 41 with serious code violations. Construct and interpret a 99% confidence interval for the true proportion of homes with serious violations.



3.An automotive company executive claims that a mean of 51.3 cars per dealership are sold each month. A major stockholder believes this is high and tests the hypothesis by sampling 35 dealerships. What conclusions can be reached if the data shows an average of 45.4 cars with a standard deviation of 15.4?



4.A manufacturing process is supposed to produce nails that are 3.25 inches in length. To test the machine producing the nails, a sample of 150 nails shows an average length of 3.17 inches with a standard deviation of 0.09. Is this significant evidence that the machine is not working properly?
 
Please show all the work and the methods used so that i may learn the step by step process and understand. Thank you
Please show all YOUR work so that we may see what methods you are using, and can guide you in the steps where you are stuck.

These all have to do with "Samples of size N." You might find something called the "sampling theorem" in your text or notes. How is the distribution of sample means related to an assumed population distribution?
 
Please show all the work and the methods used so that i may learn the step by step process and understand. Thank you


1.In a SRS of 30 subway cars during rush hour, the average number of riders per car was 82.5 with a standard deviation of 4.7 (assume the sample data was approximately normal). Establish and interpret a 90% confidence interval for the average number of riders per car during rush hour.



2.A building inspector inspects 245 homes and finds 41 with serious code violations. Construct and interpret a 99% confidence interval for the true proportion of homes with serious violations. (What type of distribution is this?)



3.An automotive company executive claims that a mean of 51.3 cars per dealership are sold each month. A major stockholder believes this is high and tests the hypothesis by sampling 35 dealerships. What conclusions can be reached if the data shows an average of 45.4 cars with a standard deviation of 15.4?



4.A manufacturing process is supposed to produce nails that are 3.25 inches in length. To test the machine producing the nails, a sample of 150 nails shows an average length of 3.17 inches with a standard deviation of 0.09. Is this significant evidence that the machine is not working properly?

Looks like you are stuck in the beginning - with no work to show. So:

What is the definition of confidence interval in statistics?

How would you use that in these problems (which formulas)?

Please share your work with us.

You need to read the rules of this forum. Please read the post titled "Read before Posting" at the following URL:

http://www.freemathhelp.com/forum/th...217#post322217

We can help - we only help after you have shown your work - or ask a specific question (e.g. "are these correct?")
 
Top