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Hypothesis testing (2 samples) 1. The Anderson’s Super Dollar had two grocery stores in Erie, Pennsylvania. The mean time customers wait in the checkout line at the Byrne Road store is 3.7 minute with a standard deviation of 0.8 minutes, for a sample of 40 customers. The mean waiting time for the I-90 store is 3.5 minutes with a standard deviation of 0.7 minutes for a sample of 45 customers. The waiting time has normal distribution. At the 0.05 significance level can we conclude there is a difference in the average of waiting times for the two stores? 2. The mean high temperature for 12 days in July in Detroit, Michigan was 88 degrees with a standard deviation of 4 degrees. The mean high temperature in Hilton Head, South Carolina for 8 July days was 91 degrees with a standard deviation of 3 degrees. The temperature has has normal distribution. At the 0.05 significance level, can we conclude that there is no difference in the average temperatures? 3. An egg farmer wanted to determine if increasing the time the lights were on in his hen house would increase egg production. For a sample of eight chickens he determined their production before and after increasing the amount of time the lights were on. The productions have normal distribution. The data are reported below. At the 0.05 significance level, has there been an increase in production? Hen Before After 1 10 7 2 8 5 3 5 6 4 2 8 5 3 8 6 7 8 7 3 10 8 3 2 4. A sample of 200 Lion Store charge customers 50 years or older showed that 20 did not pay their entire balance at the end of the month. A sample of 300 customers under 30 showed that 50 did not pay their entire balance at the end of the month. At the 0.02 significance level can we conclude that the same percent of the younger customers didn’t pay their entire balance at the end of the month? SPSS Task 1. We examine the stress level (1….5) of the students before and after the statistics exam. Before 5 5 4 4 3 3 2 3 3 4 After 4 1 3 2 2 1 2 3 2 2 At the 0.05 significance level A) Can we conclude the Mean of the stress level is 3 before the exam? B) Can we conclude the equality of the averages? Task 2. In an entrance exam we examine the reaction time (sec) of two candidates. We assume the normality of the reaction time. Can we conclude the equality of the averages? Candidate 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 Reaction 0,68 0,72 0,66 0,75 0,73 0,7 0,76 0,69 0,78 0,81 0,84 0,77 0,85 0,84 0,86 0,82 0,83