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15. An experiment was performed to determine the effects of alcohol consumption on driving performance. Nine randomly selected volunteer respondents (aged 21 or over) are provided with alcoholic beverages and given breathalyzer tests; when their blood alcohol level reaches .08 (the legal limit in Maryland) they take a driving simulation test. Another nine volunteer respondents (also aged 21 or over) are given non-caffeinated sodas or fruit juice and then take the driving simulation test. The researcher measures performance on the driving test by counting the number of simulated obstacles with which each driver collides (the X; values found in the data tables below). Thus, the higher the number of collisions, the poorer the driving. Test the null hypothesis that the two population means are equal against the directional (one-tailed) alternative hypothesis that the "Soda/Juice" group has a lower mean number of collisions than the "Alcohol" group. Assume that the unknown population standard deviations are equal ( 1= 2). Soda/Juice Group Alcohol Group X Soda/Juice = 1.63 X Alcohol = 3.25 $2 Soda/Juice = 1.98 $2 Alcohol = 1.07 n Soda/Juice = 9 n Alcohol = 9 Step 1) Null Hypothesis-- --Ho: Alternative Hypothesis-------H1: Step 2) State the test statistic you will use for this hypothesis test. Step 3) Your level of significance (alpha) is .05. Determine the critical value and rejection region of the test statistic based on the directionality information, the alpha level, and degrees of freedom. Make sure to draw and label these values on a bell shaped curve in the space provided below: Step 4) Calculate the obtained value of the test statistic. Write the values of the statistics you will use in your calculations in the spaces provided. X Soda/Juice Group = X Alcohol Group = $2 Soda/Juice Group S' Alcohol Group n Soda/Juice Group = n Alcohol Group = Step 5) Make a decision about your null hypothesis and interpret this decision