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TAMU STAT 302 - Practice Final Exam A

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1 Practice Final Exam A- Fall 2016 A researcher was interested in studying if the severity of damage to people and/or property involved in an accident is associated with the type of vehicle(s) involved in the accident. He obtained the following data from the National Highway Traffic Safety Administration for accidents that occurred in 1999. The data was used to determine if there was statistical evidence of an association between type of vehicle and crash severity. Assume this data came from a SRS. Use it answer next 2 questions. Property Counts Fatal Injury Damage Only Total Passenger Car 2067 221,471 99,046 322,584 Light Truck 2026 139,696 69,859 211,581 Busses 21 1825 603 2,449 Total 4114 362,992 169,508 536,614 Chi-Square Statistic P-value Likelihood ratio <.00001 Pearson  < 0.0001 1) Which of the following can be concluded from the above output when the significance level is .05? a) The data provides very strong statistical evidence, at the .05 significance level, that for people involved in accidents, there is an association between the severity of damage to people and/or property involved in an accident and the type of vehicle(s) involved in the accident. b) The data provides very strong statistical evidence, at the .05 significance level, that for people involved in accidents, the difference in the severity of damage to people and/or property is caused, in part, by differences in the type of vehicle involved in the accident. c) The data provides very strong statistical evidence at the .05 significance that more cars are involved in accidents than busses. d) The data does not provide statistical evidence, at the .05 significance level, there is an association between the severity of damage to people and/or property involved in an accident and the type of vehicle(s) involved in the accident. e) None of above. 2) What is the relative risk of an accident leading to a fatality for light trucks compared to passenger cars and how should this number be interpreted? a) The relative risk is 1.50 which means light trucks are 1.5 times more likely to be involved in fatal crashes than passenger cars. b) The relative risk is 0.98 which means light trucks and cars are about equally likely to be involved in fatal crashes. c) The relative risk is 0.66 which means light trucks are 0.66 times as likely to be involved in fatal crashes than passenger cars. d) The relative risk is 1.344 which means light trucks are 1.344 times more likely to be involved in fatal crashes than passenger cars. e) The relative risk is -0.003 which means light trucks are not likely to be involved in fatal crashes23Scatter plot of HEC vs HGMF -10123-1 0 1 2 3HGMF HEC The concentration of E. Coli in beef is tested in the laboratory using a method called HGMF. A new method that can be done in the field called HEC has been developed. A comparison of treatments needs to be done. The developers of the HEC method want to test their theory that HGMF readings and HEC readings are positively linearly related. To test their theory, they randomly selected 18 pieces of beef and measured the E. Coli concentration on each piece using both the HGMF and HEC methods. Use this to answer the next 3 questions. Regression Table Coefficient t-Value P-value Constant 0.09 -0.78 0.4445 HGMF 0.92 3.23 0.0052 3) What hypothesis should he use to test his claim? a) H0: p = 0 HA : p > 0 b) H0: 0 = 0 HA : 0 > 0 c) H0: 1 = 0 HA : 1 > 0 d) H0: = 0 HA :  > 0 e) H0: b1 = 0 HA : b1 > 0 4) What is the correct P-value the researchers should use to determine whether or not to reject the null hypothesis? a) 0.4445 b) 0.22225 c) 0.0052 d) 0.0026 e) None of the above is correct. 5) Suppose the model assumptions for linear regression are satisfied. What is the best interpretation of the slope of the regression line? a) The estimated average change in HGMF when HEC increases by 1 is 0.92. b) The estimated average change in HGMF when HEC increases by 1 is -0.09. c) The estimated average change in HEC when HGMF increases by 1 is 0.92. d) The estimated average change in HEC when HGMF increases by 1 is -0.09. e) The estimated average change in HEC when HGMF increases by 1 is 08.45. 6) A P-value equal to 0.0003 for the Chi Square Test of Independence for two categorical variables means . . . a) There is strong evidence of an association between two variables. b) There is evidence of a strong association between two variables. c) There is strong evidence of a strong association between two variables. d) There is strong evidence of independence between two variables. e) None of the above.4A wheat farmer does a study to test the theory that the average germination time for variety A wheat is greater than the average germination time of variety B wheat. He takes a random sample of size 35 of variety A type seeds and a random sample of size 35 of variety B type seeds and records how long (in hours) it takes each seed to germinate. Set  = 0.05. Use the statistical output below to answer the next 2 questions. Level Number Mean Std DevA 35 67.880 15.393B 35 76.700 14.808 t Test Comparing B - A Assuming un-equal variances Difference 8.820 t Ratio 2.443Std Err Dif 3.610 DF 67.9Upper CL Dif 16.020 Prob > |t| 0.0172Lower CL Dif 1.615 Prob > t 0.0086Confidence 0.95 Prob < t 0.9914 7) Assuming the conditions are met, what hypotheses should the researcher test? a) H0: d =  and HA: d < 0 where µd = mean difference in yield calculated as variety A minus variety B b) H0: d =  and HA: d > 0 c) H0: AB = 0 and HA: A - B < 0 where µA = mean yield of variety A, µB = mean yield of variety B d) H0: AB = 0 and HA: A - B 0 e) H0: AB = 0 and HA: A - B > 0 8) Suppose the conditions are met for using two independent samples T test to analyze these hypotheses, what is the correct P-value? a) 0.0172 b) 0.0086 c) 0.9914 d) 0.05 e) 0.95 9) In conducting a randomized comparative experiment, an experimenter will often include a group of subjects, known as a control group, to receive a fake treatment. What is the reason such a control group might be included in the experiment? Select the best answer. a) To increase the number of subjects and hence increase the sensitivity of the experiment


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