You have been hired as a marketing consultant to Johannesburg Burger Supply, Inc., and you wish to come up with a unit price for
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So on this case the 95% confidence interval would be given by (11.393;15.857)
Step-by-step explanation:
Previous concepts
A confidence interval is "a range of values that’s likely to include a population value with a certain degree of confidence. It is often expressed a % whereby a population means lies between an upper and lower interval".
The margin of error is the range of values below and above the sample statistic in a confidence interval.
Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".
Data: 14, 10, 13, 16, 12, 18, 15, 11
We can calculate the sample mean and deviation with the following formulas:
represent the sample mean
population mean (variable of interest)
s=2.669 represent the sample standard deviation
n=8 represent the sample size
Calculate the confidence interval
The confidence interval for the mean is given by the following formula:
(1)
In order to calculate the critical value we need to find first the degrees of freedom, given by:
Since the confidence is 0.95 or 95%, the value of and
, and we can use excel, a calculator or a table to find the critical value. The excel command would be: "=-T.INV(0.025,7)".And we see that
Now we have everything in order to replace into formula (1):
So on this case the 95% confidence interval would be given by (11.393;15.857)