An engineer wishing to obtain the speed characteristics on a bypass around her city at a confidence level of 95%, and an acceptable error limit of ± 2.0 mi/h, collected a total of 104 spot speed observations and determined that the standard deviation is 4.8 mi/h. Has the engineer met with all of the requirements of the study?
What will be an ideal response?
This can be answered using Equation 4.5 to determine whether minimum sample
size requirements are met.
For the 95% confidence level, z = 1.96
The acceptable margin of error, d =2
The standard deviation ? = 4.8
The minimum sample size is 23 observations. Since 104 were collected, the data collection requirements are met. Fewer observations would decrease time spent in the field and associated costs.
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