stat

Lab 1: Hypothesis Tests

Stat 244 Spring 2015 due at Week 4 recitation

This lab must be done by yourself. Your name MUST be typed into the Excel spreadsheet (not hand- written on the printout).

The example shown below does not use the actual data set. The real assignment is at the end.

In this example, an item has been purchased from 10 different retail shops. We wish to test the hypothesis that the population mean price is greater than 3 dollars. The screen capture shown below shows the formu- las that were entered into column E to generate the numbers that you see there.

The first three entries just calculate n, x , and s. The next entry is the standard error, which is the name of

( n )the quantity s

that is used in the denominator of the test statistic.

The entry next to “mu zero” should be the value that would appear in the null hypothesis. Since we are test-

ing to see if the population mean is greater than 3, our null hypothesis would have been H0:

3 , so the

number “3” appears there. Next to the word “tails”, you would enter “1” for either the upper or lower 1- sided test, or “2” for a 2-sided test.

The p-value is found using the Excel function called TDIST. This function requires 3 pieces of information. The first item is the absolute value of the test statistic. The second item is the number of degrees of free- dom, and the final item tells the function whether or not to double the area under the curve. The TDIST function then finds the area under the curve, to the right of the absolute value of the test statistic, and dou- bles that area for 2-sided tests.

Lab 1 (due at Week 4 recitation)

Using the method described above, and the data set called “gas2015.xlsx”, test to see if there is evidence

that the population mean price for a gallon of gas differs from $2.50. Use 0.05.

output fits on a single page. Turn in the printed copy. Make sure to include:

1. your null and alternative hypotheses, in the correct format

2. your decision (Reject H0 or Fail to Reject H0)

3. in your own words , a final statement interpreting that decision. Your name and these three items must be typed on the printed copy.

Make sure that your