Class Examples: Confidence Intervals for One Proportion
Please complete the following questions either by hand or typing answers into provided response locations.
When asked to use R to calculate values, or to construct a plot, copy and paste both the values or plot and the R
command you used to obtain the values or plot. Show work where appropriate.
1.
When a light turns yellow, should you stop or go through it? The article “Evaluation of Driver Behavior in
Type II Dilemma Zones at High-Speed Signalized Intersections” (
Journal of Transportation Engineer-
ing)
defines the “indecision zone” as the period when a vehicle is between 2.5 and 5.5 seconds away
from an intersection. It present observations of 710 vehicles passing through various intersections in
Vermont for which the light turned yellow in the indecision zone. These 710 vehicles can be considered
a representative example of the population. Of the 710 vehicles, 89 ran a red light.
A.
What is the parameter of interest in this situation?
B.
Calculate the sample proportion
^
p
.
C.
Check the conditions to perform a confidence interval for this situation.
D.
If you want to calculate a 90% confidence interval for
p
, calculate the appropriate value of
z
/2
to
six decimal places.
1
