Question

IV. In a study of driving practices in Strathcona County, Alberta, Canada, it was found that 48% of drivers did not stop at intersections with stop signs on county roads (Edmonton Journal, July 19, 2000) . Assume that a follow-up study conducted two months later found that 360 of 800 drivers did not stop at intersections with stop signs on county roads. Perform an analysis assuming that the objective of the follow-up study is to see if the proportion of drivers who do not obey the stop signal changed, with a 2.5% margin of error.

Answer 1

Number of Items of Interest,   x =   360
Sample Size,   n =    800
      
Sample Proportion ,    p̂ = x/n =    0.4500

Confidence Interval is p̂ ± E = 0.45±0.025= (0.425, 0.475)

Ho :   p =    0.48
H1 :   p ╪   0.48

since, confidence interval do not contain 0.48, reject the null hypothesis,

there is enough evidence to conclude that true  proportion of drivers who do not obey the stop signal has changed