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 personhours 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. O’Connor, and K. Varghese, Journal of Management Engineering, 1995:4147). Each value represents an average of several projects, and two outliers have been deleted.
Person Hours (X) 
Cost(Y) 
Person 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 leastsquares line for predicting y from x.
b. Plot the residuals versus the fitted values. Does the model seem appropriate?
c. Compute the leastsquares 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 personhours of labor.
Chapter 9: Multivariate Designs  Means many variables  Study more than 2 variables in a single study  Enhance understanding of bivariate associations Longitudinal design  Measures same variables and same sample at several time points  Use to assess variable relationships across time  Use to see variable stability across time  3 types of correlations assessed o Cross sectional: two variables measured at the same point in time [bivariate correlations] o Autocorrelations; testing variable against itself measured at two time points. o Crosslag correlations; early measure of one variable against later measure of the other variable Moderation Language  Violence