Virginia Department of Transportation traffic engineers were compelled to measur

Question

Virginia Department of Transportation traffic engineers were compelled to measure the speed of traffic on a residential street in a Northern Virginia suburb because the residents complained enough to their elected officials about speeding vehicles on their street. Reluctantly, the en- gineers measured the speeds of the motor vehicles and from 1,729 vehicles in 24 hours, they reported that the average speed was 28 MPH. Since the posted speed limit is 25 MPH, the en- gineers concluded that “the traffic conforms to the posted speed limit”; therefore, no remedial action was taken. However, some residents obtained the raw traffic data and discovered that the speeds of three vehicles exceeded 65 MPH, that 15% of the vehicles traveled faster than 40 MPH, and that 80% exceeded 25 MPH. If you are a state legislator representing the community, would you conclude that both factions or one of them or neither were distorting the truth with descriptive statistics? Explain. (All of the numbers are reliable.)

Explanation / Answer

Assuming a normal distribution, a population of vehicles has an average speed of 28 MPH.

1. In that case, 50% of vehicles have speed more than 28 MPH. However, the descriptive statistics tells that 80% of the vehicles have speed more than 25 MPH. This implies that the average speed of vehicles is much higher than 28 MPH. This is not true according to the traffic engineers. Thus, the statistics about 80% exceeding 25 MPH is distorting the truth

2. It is possible to have 15% of vehicles travelling faster than 40 MPH. This is because 15% is a small number to pull up the average speed much above 28 MPH

Related Questions

Navigate

• Browse (All)
• Browse V
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.