Numbers of children studied
| FPHVS bases | Comparison bases | |||||||
|---|---|---|---|---|---|---|---|---|
| A | B | C | W | X | Y | Z | Totals | |
| Movers = moved out of Avon before 2 years old. | ||||||||
| Duplicates = child in more than one study base. | ||||||||
| Retrospective data | ||||||||
| Initial no. | 287 | 692 | 301 | 283 | 436 | 232 | 208 | |
| Movers | 18 | 47 | 7 | 10 | 9 | 12 | 5 | |
| Duplicates | 38 | 76 | 28 | 17 | 15 | 32 | 6 | |
| Deceased | 1 | 0 | 1 | 0 | 3 | 1 | 0 | |
| Adjusted no. | 230 | 569 | 265 | 256 | 409 | 187 | 197 | |
| Total | 1064 | 1049 | ||||||
| Prospective data | ||||||||
| No. contacted | 166 | 104 | 55 | 192 | 97 | 60 | 59 | 733 (100%) |
| Initial refusals (% no. contacted) | 56 (34%) | 35 (34%) | 22 (40%) | 67 (35%) | 36 (37%) | 17 (28%) | 25 (42%) | 258 (35%) |
| Initial acceptance (% no. contacted) | 110 (66%) | 69 (66%) | 33 (60%) | 125 (65%) | 61 (63%) | 43 (72%) | 34 (58%) | 475 (65%) |
| Subsequent refusals | 4 | 3 | 0 | 6 | 3 | 0 | 0 | 16 |
| Final no. in study (% no. contacted) | 106 (64%) | 66 (64%) | 33 (60%) | 119 (62%) | 58 (60%) | 43 (72%) | 34 (58%) | 459 (63%) |
| Total | 205 | 254 | ||||||