Good forecasting and control of preconstruction activities leads to more efficient use of time and resources in highway construction projects. Data on construction costs (in $1000s) and person-hours of labor required on several projects are presented in the following table and are taken from the article Forecasting Engineering Manpower Requirements for Highway Preconstruction Activities (K. Persad, J. OConnor, and K. Varghese, Journal of Management Engineering, 1995:4147). Each value represents an average of several projects, and two outliers have been deleted. Person- PersonHours (x) Cost (y) Hours (x) Cost (y) 939 251 1069 355 5796 4690 6945 5253 289 124 4159 1177 283 294 1266 802 138 138 1481 945 2698 1385 4716 2327 663 345 a. Compute the least-squares line for predicting y from x. b. Plot the residuals versus the fitted values. Does the model seem appropriate? c. Compute the least-squares line for predicting ln y from ln x. d. Plot the residuals versus the fitted values. Does the model seem appropriate? e. Using the more appropriate model, construct a 95% prediction interval for the cost of a project that requires 1000 person-hours of labor.
Components of Statistics Collecting and analyzing data in order to create a reliable sample. ● Population: The units involved in an issue an individual is interested in investigating. Typically, entire populations are too large to measure. ○ Students at the University of Illinois are a population. ● Sample: a smaller set of individual units selected from the investigation.Sampling solves the issue of large numbers, but it will also cause uncertainty. Aspects of the sample do not always correlate with the vast majority. ○ Individuals that are in statistics classes are a sample of the students at the University. ● Statistics: This is where the sample is used. The purpose of statistics is better understand the populati