Dr. Palese placed eight guinea pigs in a temperature-controlled chamber, one of which was infected and the others were not. The number of guinea pigs that became infected was used to measure the rate of transmission. By varying air temperature in the guinea pigs鈥?quarters, they discovered that transmission was excellent at 41 degrees. It declined as the temperature rose until, by 86 degrees, the virus was not transmitted at all.
The animals also released viruses nearly two days longer at 41 degrees than at a typical room temperature of 68 degrees.|||The way it is described, there is no control group.
Now if the doctor had put a few guinea pigs, none of which were infected (*) in a chamber, and cycled the temperature the same way, that would have been a control group.
(*) Actually, we would _assume_ that none were infected. The testing for that would never be 100% accurate.|||The first response is correct. In this design there is no separate control group. It is known as a within-subjects design, where you put the same subject (animal, human, whatever you're testing) into different situations in which you change only a particular controlled aspect between the environments.
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