Variables: Weight - Known combined weight of the truck and load Pre-Calib -Weigh
ID: 3353655 • Letter: V
Question
Variables:
Weight - Known combined weight of the truck and load
Pre-Calib -Weight of the truck & load on the in-motion scale prior to calibration
Post-Calib - Weight of the truck and load on the in-motion scare after calibration
1a. Can we use the study to make inferences about the scale's accuracy to the population of all two-axle, six-tire trucks?
2b. Why were ten different loads for the truck used in the study?
Roads that carry mostly car traffic experience different types of damage than those frequented by larger trucks. The maintenance costs can be minimized if roads are properly designed to handle its primary type of traffic. In recent years intelligent transportation systems have been developed that allow to check whether passing trucks exceed a specified weight. The systems can also be used to determine primary type of traffic handled by a particular road. In 1981, the Minnesota Department of Transportation installed a scale into the surface of an interstate highway to weigh vehicles as they drove over. The Department of Transportation planned to use the scale to gather information on the number and weights of vehicles that used this stretch of highway and use the information in the planning and design of future highways. To test the scale's accuracy, a single two-axle, six-tire truck was used to compare measurements from the in-motion scale to measurements made on a standard scale. The truck was filled with one of ten different loads of known weight so that the actual combined weight of the truck and the load was known. The truck was then driven across the scale in the road to get the in motion measurement. This experiment was then repeated for the other nine loads. After some analysis of this first set of measurements, the weight-in-motion scale was recalibrated and the weights of the truck with the same ten loads were measured again with the in-motion scale.Explanation / Answer
1a. Yes, we can use the study to make inferences about the scale's accuracy to the population of all 2-axle,6-tire trucks because by recalibration excercise, it is ensured that if there existed any systematic error in the in-motion scale, it has been corrected for, and hence, the variations in the in-motion scale measurements post calibration can now be attributed purely to the in-motion scale's lack of accuracy and not any other factor.
2b. Ten different loads were used to ensure that the sample data which is collected from this simulated experiment, is sufficiently representative of the true population characteristics. By using 10 different loads, we have taken into account the fact that on the actual road condition, the different trucks will be of slightly different weights. Therefore, we have tried to represent the true population characteristic into our sample data.
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