of 271 studies undertaken with animals (rats, mice and primates) showed that only 59% of the studies stated the objective of the study and the number and characteristics of the animals used, most of the papers surveyed did not use randomization (87%) or blinding (86%) to reduce bias in animal selection and outcome assessment, and only 70% of the publications that used statistical methods described their methods and presented the results with a measure of error or variability.
In , animal trials of a potential stroke drug looked very promising. The drug, however, did not work in clinical trials. When the reasons were investigated it appeared that the animal tests may not have robust enough, with no blinding or randomization. Tests which include no reported randomization are 5 times more likely to render a positive result than those that are conducted against rigorous guidelines.