Table 1.
| Study Characteristics |
Moderate–Impact-Factor Group |
High–Impact-Factor Group | P | ||||||
|---|---|---|---|---|---|---|---|---|---|
|
AJOG (n=56) |
BJOG (n=52) |
Obstet Gynecol (n=51) |
Total (n=159) |
JAMA (n=51) |
Lancet (n=52) |
NEJM (n=51) |
Total (n=154) |
||
| Number of authors | |||||||||
| 1–4 | 16 (29) |
25 (48) |
16 (31) | 57 (36) | 13 (25) | 8 (15) | 2 (4) | 23 (15) | <.001 |
| 5–9 | 34 (60) |
27 (52) |
33 (64) | 94 (59) | 17 (33) | 25 (48) | 19 (38) |
61 (40) | |
| 10 or more | 6 (11) | 0 | 2 (4) | 8 (5) | 21 (41) | 19 (37) | 30 (58) |
70 (45) | |
| Hypothesis clearly stated? |
16 (29) |
4 (8) | 13 (26) | 33 (21) | 11 (22) | 6 (12) | 17 (33) |
34 (22) | .6 |
| Negative study | 12 (21) |
6 (12) | 4 (8) | 22 (14) | 11 (22) | 6 (12) | 10 (20) |
27 (18) | .4 |
| Sample size/power calculations |
9 (16) | 11 (21) |
16 (32) | 36 (23) | 22 (43) | 18 (35) | 33 (65) |
73 (47) | <.001 |
| Statistical measures | |||||||||
| Recommended reporting in abstract | 14 (25) |
16 (31) |
28 (55) | 58 (36) | 30 (59) | 32 (62) | 32 (63) |
94 (61) | <.001 |
| Recommended reporting in article | 33 (60) |
30 (58) |
41 (80) | 104 (65) |
41 (80) | 42 (81) | 46 (90) |
129 (84) |
.002 |
| P-values given for NS differences* | 36 (92) |
21 (73) |
41 (95) | 99 (88) | 38 (95) | 33 (100) |
42 (95) |
113 (97) |
.04 |
| Regression analysis performed? |
29 (52) |
19 (37) |
28 (55) | 76 (48) | 27 (53) | 29 (56) | 36 (71) |
92 (60) | .03 |