What is the biggest error, methodologically, in the following scientific study? "The goal of the study was to determine whether the ebola virus is as deadly in rhesus monkeys as it is in gorillas. I took a sample of four healthy rhesus monkeys and four healthy gorillas. The animals were a random mixture of sexes and ages. I arranged eight cages so that each animal would be in a separate cage, and I made sure there would be no contact among the cages that would allow transmission of the virus. Then I obtained a sample of the ebola virus from the National Institute of Infectious Diseases and injected all the monkeys and gorillas with the same size dose. At the end of four days, I noticed that all the gorillas were dead but only one of the monkeys was dead. An autopsy revealed that three of the four gorillas had died of ebola fever but that the fourth, nicknamed Curious George, had died of internal bleeding after swallowing the small pair of scissors that were left within reach of its cage. The dead monkey had died of ebola fever. At the end of two months there were no more deaths. I concluded that my dosage of the ebola virus is three times as likely to be deadly to gorillas as it is to rhesus monkeys, but I recommended repeating the study to see if the percentages of deaths due to ebola fever remained steady over a wide range of dosages of the virus."