1 / 8

Transportation Planning

Transportation Planning. CE 573 Lecture 5. Topics. Data collection issues Sample size estimation Statistical inference. Data Collection. Location Cordon Screen line Isolated point Time Peak Off-peak Days of week Days of year. Survey instrument Questions Device Personnel

zasha
Download Presentation

Transportation Planning

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Transportation Planning CE 573 Lecture 5

  2. Topics • Data collection issues • Sample size estimation • Statistical inference

  3. Data Collection • Location • Cordon • Screen line • Isolated point • Time • Peak • Off-peak • Days of week • Days of year • Survey instrument • Questions • Device • Personnel • Work shifts • Individual capabilities • Communications

  4. Sample Size Terminology • Mean ( ) • Sample standard deviation (sx) • Sample size (n) • Confidence level (α) • Confidence interval limits (+/-Δ) • Test statistic (t) • Population size (N) • More help: http://edis.ifas.ufl.edu/PD006

  5. Sample Size • Test statistic • Critical value (see table given α/2 and degrees of freedom) n-1 • Calculated value  • Confidence interval limit as proportion of the mean  • n  

  6. Sample Size Adjustment • Adjusting for small population size (N) • Redefine n as n’, with n being the adjusted sample size • n’  unadjusted population size calculated • n  adjusted population size

  7. Survey Scenario • What kind of sampling should you do? • Random or • Stratified random • Depends on • Cost of sending survey • Cost of processing survey

  8. Survey Scenario • Say n must be at least 50 for each cell or population category • Random sample • Smallest proportion  0.05 • Total sample size is 50/0.05 = 1,000 observations • Stratified sample • Preliminary survey of 1,000 • Get addresses of 50 households in each cell • Total sample size is 4 * 50 = 200 (50 for each cell) • Do you need to adjust the sample size by cell?

More Related