LAB 11 Instructions and Questions for Excel 2007 MATCHED PAIR T TEST TWO SAMPLE T TEST NAME LAB TIME LAB BLDG PART 1 MATCHED PAIR T TEST 1 2 3 4 5 Go to the Stat 301T webpage and open the Lab 11 Data file The data for the MATCHED PAIR T TEST is in the upper left corner columns A C A matched pair t test was designed to determine whether the fuel economy using Gasoline A is different from the fuel economy using Gasoline B There was no prior information on which brand would give better mileage Write the null and alternate hypothesis for this test 6 Ho Ha 7 8 9 10 11 15 vehicles were selected for the test The driver of each vehicle was instructed to use three tanks of one brand keep records of the miles per gallon and then do likewise using three tanks of the other brand The starting gasoline for each driver vehicle combination was randomly assigned The miles per gallon for each vehicle are shown in Columns B and C In Column D calculate the difference Column C Column B for each line of the data In D22 calculate the mean for column D Col D mean 12 In D23 calculate the standard deviation for column D Std Dev 13 14 15 In D24 enter D22 This is the numerator of the test statistic for this test In D25 enter D23 SQRT 15 This is the denominator for the test statistic for this test In D26 enter D24 D25 This is the test statistic for this test Record the test statistic 16 In D27 we will now determine the P Value Enter and get the function TDIST and in the new window enter D26 for x Enter 14 for the degrees of freedom n 1 and enter 2 for the number of tails because it is a two side test Click OK Record the P Value If 05 what decision should be made regarding Ho 17 18 Reject Ho 19 OR Do not reject Ho What decision would be made if 01 PART 2 TWO SAMPLE T TEST 20 21 22 A two sample t test was designed to determine whether the fuel economy using Gas A is different from the fuel economy using Gas B There was no prior information on which brand would give better mileage 30 vehicles were selected for this test 15 would use Gas A and the other 15 would use Gas B 23 Write the null and alternate hypothesis for this two sample t test 24 Ho Ha 25 26 27 28 29 30 31 32 33 34 Refer to the two sample t test data in columns G J Note that the data in column H matches the data in column B and that the data in column J matches the data in column C However the vehicles in column G are not the same vehicles as those in column I and therefore it does not make sense to calculate line by line differences The only comparison that can be made is to compare the overall mean and standard deviation for column H to the overall mean and standard deviation for column J In H22 calculate the mean for Column H In H23 calculate the standard deviation for Column H In J22 calculate the mean for Column J In J23 calculate the standard deviation for Column J In J24 calculate the numerator of the test statistic for this test as follows J22 H22 In J25 calculate the denominator of the test statistic for this test SQRT H23 2 15 J23 2 15 In J26 calculate the test statistic for this test J24 J25 Record the test statistic 35 In J27 calculate the two side P value as follows TDIST J26 14 2 and record the answer P value 36 If 05 what decision should be made regarding Ho Reject Ho 37 OR Do not reject Ho Notice that we reach a different decision in the two sample t test compared with the matched pair t test even though the data being compared uses the same numbers We still see the same difference in the MPG between the two brands of gasoline Why did the test statistic Pvalue and decision come out different
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