A random sample of 25 round trip flights between Philadelphia and Dallas has an average airfare of 393.50 with a sample Standard Deviation of $50.30. The critical value for an 80% confidence interval around this sample mean

And the confidence interval would be given by:

Step-by-step explanation:

Information given

represent the sample mean

population mean

s=50.30 represent the sample standard deviation

n=25 represent the sample size  

Confidence interval

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

  (1)

The degrees of freedom are given by:

The Confidence level is 0.80 or 80%, the value of significance and , the critical value for this case would be:

And the confidence interval would be given by:

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step-by-step explanation: