1. The generality of conclusions from well controlled experiments can often be tested by comparative studies. 2. The theory has not yet been tested by a properly controlled experiment. 3. Two of the four specimens known to be infected with M tuberculosis were positive in the controlled experiment. 4. Of course, in a controlled experiment, where randomization is possible, we are perfectly entitled to combine the advantages of randomization and matching. 5. And controlled experiments often prove observational studies wrong. 6. Aristotle failed to see the value of controlled experiment, believing that nature could only be understood whole. 7. A controlled experiment was in order. 8. But the most valid treatments and findings come from controlled scientific experiments that can be independently repeated or verified. 9. By the middle of the decade, a number of controlled experiments had found no cold-preventive benefits from vitamin C. 10. He has ignored the results of five national surveys, and now rejects the findings of two years of controlled experiment. |