SOLVING THE CONFIDENCE INTERVAL FOR THIS PROBLEM..

J

jw4833

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Mar 19, 2011
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16
Hello...

I was in the middle of completing a weekly quiz for my Statistics class and I got a message stating that the server was disconnected and to try again later...

However, I got somewhat confused on how the tutorial derive at the confidence interval example that was instructed to follow in order to do the problem. This was the example:

1.96 x 21.50 sqrt 70 = 5.04...I did not get this amount and I could not figure out how the tutorial got this. Because this is what I got; 1.96 x 21.50 divide sqrt. 70 = 0.602

This is the problem that I got stuck on;

As a part of your study, you randomly select 45 repair costs and find the mean to be $139.00. The sample standard deviation is $19.10. Complete parts (a) and (b)

(a) Construct a 95% confidence interval for the population mean repair cost.

The 95% confidence interval is ______________________

Now, I know that the confidence interval value of c is 0.95

95% = 1.96 so..this is where my confusion starts because I thought you had to do this;

1.96 x 19.10 sqrt. 45 = (to divide) therefore, my answer was 0.8319

So, could you please show me what I am doing wrong?
 
jw4833 said:
Hello...

I was in the middle of completing a weekly quiz for my Statistics class and I got a message stating that the server was disconnected and to try again later...

However, I got somewhat confused on how the tutorial derive at the confidence interval example that was instructed to follow in order to do the problem. This was the example:

1.96 x 21.50 sqrt 70 = 5.04...I did not get this amount and I could not figure out how the tutorial got this. Because this is what I got; 1.96 x 21.50 divide sqrt. 70 = 0.602

You are making calculator mistake.

21.5/?(70) = 2.56974151

and

2.56974151 * 1.96 = 5.03669336

Another thing: Do not use 'x' for multiplication operator - use '*' instead.
This is the problem that I got stuck on;

As a part of your study, you randomly select 45 repair costs and find the mean to be $139.00. The sample standard deviation is $19.10. Complete parts (a) and (b)

(a) Construct a 95% confidence interval for the population mean repair cost.

The 95% confidence interval is ______________________

Now, I know that the confidence interval value of c is 0.95

95% = 1.96 so..this is where my confusion starts because I thought you had to do this;

1.96 x 19.10 sqrt. 45 = (to divide) therefore, my answer was 0.8319

So, could you please show me what I am doing wrong?
Click to expand...
 
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