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 Counts Passenger Car Light Truck Busses Total Chi Square Statistic Likelihood ratio Pearson 1 Fatal 2067 2026 21 4114 Injury 221 471 139 696 1825 362 992 Property Damage Only 99 046 69 859 603 169 508 Total 322 584 211 581 2 449 536 614 P value 00001 0 0001 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 crashes 1 2 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 Constant HGMF 3 Scatter plot of HEC vs HGMF Coefficient t Value P value 0 09 0 92 0 78 3 23 0 4445 0 0052 What hypothesis should he use to test his claim a b H0 p 0 HA p 0 H0 0 0 HA 0 0 c d e H0 1 0 HA 1 0 H0 0 HA 0 H A b1 0 H0 b1 0 3 2 HEC Regression Table 1 0 1 1 0 1 2 3 HGMF 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 b c d e There is strong evidence of an association between two variables There is evidence of a strong association between two variables There is strong evidence of a strong association between two variables There is strong evidence of independence between two variables None of the above 3 A 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 A B Number 35 35 Mean 67 880 76 700 Std Dev 15 393 14 808 t Test Comparing B A Assuming un equal variances Difference Std Err Dif Upper CL Dif Lower CL Dif Confidence 7 8 820 3 610 16 020 1 615 0 95 t Ratio DF Prob t Prob t Prob t 2 443 67 9 0 0172 0 0086 0 9914 Assuming the conditions are met what hypotheses should the researcher test a b c d e H0 H0 H0 H0 H0 d d A A A and HA d 0 where d mean difference in yield calculated as variety A minus variety B and HA d 0 B 0 and HA A B 0 where A mean yield of variety A B mean yield of variety B 0 B 0 and HA A B 0 and H 0 B A A B 8 Suppose the conditions are met for using two independent samples T test to analyze these hypotheses what is the correct P value a b c d e 0 0172 0 0086 0 9914 0 05 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 in detecting effects of the treatment b To gain more complete understanding of any biases that might be present in …