Bicycle accidents, alcohol, and gender. In given Exercise we examined the percent of fatally injured bicyclists tested for alcohol who tested positive. Here we examine the same data with respect to gender.
|
Gender
|
n
|
X(tested positive)
|
|
Female
|
191
|
27
|
|
Male
|
1520
|
515
|
(a) Summarize the data by giving the estimates of the two population proportions and a 95% confidence interval for their difference. Briefly summarize what the data show.
(b) Use a test of significance to examine whether the two proportions are equal.
Exercise
Bicycle accidents and alcohol. In the United States approximately 900 people die in bicycle accidents each year. One study examined the records of 1711 bicyclists aged 15 or older who were fatally injured in bicycle accidents between 1987 and 1991 and were tested for alcohol. Of these, 542 tested positive for alcohol (blood alcohol concentration of 0.01% or higher).
(a) Summarize the data with appropriate descriptive statistics.
(b) To do statistical inference for these data, we think in terms of a model where p is a parameter that represents the probability that a tested bicycle rider is positive for alcohol. Find a 99% confidence interval for p.
(c) Can you conclude from your analysis of this study that alcohol causes fatal bicycle accidents? Explain.
(d) In this study 386 bicyclists had blood alcohol levels above 0.10%, a level defining legally drunk in many states at the time. Give a 99% confidence interval for the proportion who were legally drunk according to this criterion.