TABLE 1 - Comparison of Sampling Strategies
TABLE 1 - Comparison of Sampling Strategies
| Sampling and estimation alternative | Unstratified ratio estimation statistics | Overall performance | ||||
|---|---|---|---|---|---|---|
| cv of pass-miles | cv of auxiliary variable | Correlation coeff between pass-miles and auxiliary variable | Unit cv | Necessary sample size (SS) | SS reduction vs. Circular | |
| – Circular 2710.1A | n.a. | 549 | ||||
| A Direct sampling and estimation | 0.95 | 522 | 5% | |||
| B Ratio estimation; auxiliary variable = boardings | 0.95 | 0.77 | 0.67 | 0.72 | 296 | 46% |
| C Stratified ratio estimation (4 strata); auxiliary variable = boardings | 0.43 | 117 | 79% | |||
| D Combined ratio estimation; auxiliary variable = boardings | 0.45 | 117 | 79% | |||
| E Ratio estimation; auxiliary variable = (boardings * route length) | 0.95 | 0.91 | 0.89 | 0.44 | 112 | 80% |
| F Ratio estimation; auxiliary variable = (boardings * adjusted route length) | 0.95 | 1.09 | 0.89 | 0.51 | 147 | 73% |
| G Combined ratio estimation; auxiliary variable = (boardings * route length) | 0.39 | 86 | 84% | |||
KEY: cv = coefficient of variation.