14. In 1996, 31 states in the country increased their maximum allowable highway speed limit. The following question refers to data for 38 states from years 1994 and 1998. After is a binary variable that indicates whether the data are from 1998, StateChanged Law is a binary variable that indicates whether the state increased their maximum allowable highway speed limit in 1996 (which is in between 1994 and 1998), and TrafficFatalities is the number of traffic fatalities. Dependent Variable: TrafficFatalities After StateChanged Law After x StateChanged Law 15.3 (476.0) 410.6 (382.5) 12.2 (540.9) 467.1 (336.6) 0.0395 62 Intercept R2 N (e) What doesn't the differences-in-differences estimator control for? (f) Do you think that failure to "randomize" is a concern? Define this term and propose a reason for why this may be a concern in the study. (8) Do you think that failure to follow treatment protocol is a concern? Define this term and propose a reason for why this may or may not) be a concern in the study. (h) Do you think that attrition is a concern? Define this term and propose a reason for why this may or may not) be a concern in the study. Remember that the unit of observation is the state-year, i.e. we observe multiple states for multiple years. 14. In 1996, 31 states in the country increased their maximum allowable highway speed limit. The following question refers to data for 38 states from years 1994 and 1998. After is a binary variable that indicates whether the data are from 1998, StateChanged Law is a binary variable that indicates whether the state increased their maximum allowable highway speed limit in 1996 (which is in between 1994 and 1998), and TrafficFatalities is the number of traffic fatalities. Dependent Variable: TrafficFatalities After StateChanged Law After x StateChanged Law 15.3 (476.0) 410.6 (382.5) 12.2 (540.9) 467.1 (336.6) 0.0395 62 Intercept R2 N (e) What doesn't the differences-in-differences estimator control for? (f) Do you think that failure to "randomize" is a concern? Define this term and propose a reason for why this may be a concern in the study. (8) Do you think that failure to follow treatment protocol is a concern? Define this term and propose a reason for why this may or may not) be a concern in the study. (h) Do you think that attrition is a concern? Define this term and propose a reason for why this may or may not) be a concern in the study. Remember that the unit of observation is the state-year, i.e. we observe multiple states for multiple years