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#1 2008-12-12 01:17:37

Prakash Panneer
Member
Registered: 2006-06-01
Posts: 110

Statistics

The cafateria was accused of cheating students bynot giving them enough coffee in their 12oz cups. 15 cups were selected randomnly, they had a mean of 11.7 with a std dev of 0.5 at 0.01 significance level the claim that the customers were being cheated.

Thanks in advance.


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#2 2008-12-17 04:36:23

mathceleb
Member
Registered: 2008-08-27
Posts: 19

Re: Statistics

Prakash Panneer wrote:

The cafateria was accused of cheating students bynot giving them enough coffee in their 12oz cups. 15 cups were selected randomnly, they had a mean of 11.7 with a std dev of 0.5 at 0.01 significance level the claim that the customers were being cheated.

Thanks in advance.

It sounds like our 0.01 significance level is our 1 - 0.01 = 99% confidence interval.  We want to check the confidence interval of a small population (< 35), so we use the Student t-test.  We have all 4 inputs to generate the math and answer:

Student T Confidence

Running the numbers, we get a sample mean of:
11.3157 < μ < 12.0843

We are 99% confident that our mean of 12 ounce cups is inside this interval, so I would say that the students are not being cheated.

Let me know if this explanation makes sense.

Also, if we would have had a large sample size (> 35), we could have used this confidence interval check here:

Normal Distribution Confidence

Last edited by mathceleb (2008-12-17 04:37:43)

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