Table 3.
Internal validity assessment: equivalence of study groups 1–3 at study’s end*
| Independent variables | Group 1, n (%) |
Group 2, n (%) |
Group 3, n (%) |
P |
|---|---|---|---|---|
| Study candidate status (n = 3865) |
.441 | |||
| Completed baseline survey only |
222 (17.4) † | 259 (19.7) | 232 (18.0) ‡ | |
| Completed all three surveys |
697 (55.1) | 726 (55.2) | 706 (55.2) | |
| Completed baseline + year 1 surveys |
124 (9.8) § | 122 (9.3)∥ | 119 (9.3) ¶ | |
| Completed baseline + year 2 surveys |
73 (5.8) | 62 (4.7) | 72 (5.6) | |
| Completed year 1 and year 2 surveys |
51 (4.0) | 54 (4.1) | 60 (4.7) | |
| Completed year 1 survey only |
30 (2.4) | 29 (2.2) | 15 (1.2) | |
| Completed year 2 survey only |
70 (5.5) | 64 (4.9) | 78 (6.1) | |
| Survey response mode # (n = 3126) |
.081 | |||
| 812 (78.5) | 834 (79.3) | 833 (80.1) | ||
| Phone | 127 (12.3) | 128 (12.2) | 96 (9.2) | |
| Mail (abbreviated survey) |
95 (9.2) | 90 (8.6) | 111 (10.7) | |
| Ever used VA health- care services (n = 3126) |
.662 | |||
| Yes | 467 (45.2) | 457 (43.4) | 452 (43.5) | |
| No | 567 (54.8) | 595 (56.6) | 588 (56.5) | |
| Sampling round ** (n = 3126) |
.990 | |||
| 1 | 541 (52.3) | 549 (52.2) | 546 (52.5) | |
| 2 | 493 (47.7) | 503 (47.8) | 494 (47.5) | |
| Age, y†† (n = 3126) | .677 | |||
| 52–64 | 717 (69.3) | 745 (70.8) | 720 (69.2) | |
| ≥65 | 317 (30.7) | 307 (29.2) | 320 (30.8) | |
VA = Veterans Administration. P values are from two-sided chi-square tests.
Two participants died less than 30 days after completing the baseline survey and were ineligible for the intervention effectiveness analysis.
Two participants died less than 30 days after completing the baseline survey and were ineligible for the intervention effectiveness analysis.
Two participants had incomplete mammography data.
Three participants had incomplete mammography data.
Two participants had incomplete mammography data.
Three thousand one hundred and twenty-six participants had complete mammography information on their year 1 or year 2 follow-up survey.
Sampling round 1 occurred on September 4, 2000 (with follow-up through December 17, 2003); sampling round 2 occurred on June 1, 2001 (with follow-up through October 1, 2004).
At baseline survey mail date.