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. O’Connor, and K. Varghese, Journal of Management Engineering, 1995:41-47). 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 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.
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 Cross-lag correlations; early measure of one variable against later measure of the other variable Moderation Language - Violence
