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tatuchka [14]
3 years ago
13

The manager of a grocery store has taken a random sample of 100 customers. The average length of time it took these 100 customer

s to check out was 4.0 minutes. It is known that the standard deviation of the checkout time is one minute. The 98% confidence interval for the average checkout time of all customers is Group of answer choices 3.02 to 4.98 3.00 to 5.00 3.795 to 4.205 3.767 to 4.233
Mathematics
1 answer:
AlladinOne [14]3 years ago
4 0

Answer:

4-2.326\frac{1}{\sqrt{100}}=3.767    

4+2.326\frac{1}{\sqrt{100}}=4.233    

So on this case the 98% confidence interval would be given by (3.767;4.233)

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".

\bar X=4 represent the sample mean

\mu population mean (variable of interest)

\sigma=1 represent the population standard deviation

n=100 represent the sample size  

Solution to the problem

The confidence interval for the mean is given by the following formula:

\bar X \pm z_{\alpha/2}\frac{\sigma}{\sqrt{n}}   (1)

Since the Confidence is 0.98 or 98%, the value of \alpha=0.02 and \alpha/2 =0.01, and we can use excel, a calculator or a table to find the critical value. The excel command would be: "=-NORM.INV(0.01,0,1)".And we see that z_{\alpha/2}=2.326

Now we have everything in order to replace into formula (1):

4-2.326\frac{1}{\sqrt{100}}=3.767    

4+2.326\frac{1}{\sqrt{100}}=4.233    

So on this case the 98% confidence interval would be given by (3.767;4.233)

   

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