Table 3.
Recall and precision of physician searches tested in PubMed and Google Scholar (within the first 40 citations, PubMed found no relevant citations for 54% of the searches and Google Scholar found no relevant citations for 21% of the searches).
| Measurea | Within first 40 citations | All citations | |||
| Mean, %b (SDc) | P valued | Mean, %b (SDc) | P valued | ||
| Recall |
|
|
<.001 |
|
.10 |
|
|
PubMed | 10.9 (20) |
|
38.0 (33) |
|
|
|
Google Scholar | 21.9 (24) |
|
43.2 (29) |
|
| Free full-text recall | <.001 |
|
<.001 | ||
|
|
PubMed | 4.7 (11) |
|
16.4 (20) |
|
|
|
Google Scholar | 14.6 (20) |
|
25.1 (23) |
|
| Precision |
|
|
.07 |
|
<.001 |
|
|
PubMed | 5.6 (11) |
|
6.0 (11) |
|
|
|
Google Scholar | 7.6 (7) |
|
0.8 (0.8) |
|
aFormulas for measures: (1) Recall: (number of relevant articles retrieved) / (total number of relevant articles available); (2) Free full-text recall: (number of relevant articles retrieved available for free full-text viewing) / (total number of relevant articles available), and (3) Precision: (number of relevant articles retrieved) / (total number of citations retrieved).
bValues represent mean of results from 100 searches.
cSD=Standard deviation.
d P values compare PubMed to Google Scholar using a paired t test; significance values remained similar when using the nonparametric Wilcoxon signed rank test.