Answer:
The correct answer to: A psychiatrist is testing a drug that treats depression. he has given the drug to all his patients and all of them have experienced a decrease in depressive symptoms. although this is interesting, his experience is limited because he does not have a: Is: A comparison group that did not receive the drug.
Explanation:
All right, so in this question, we are analyzing a situation in which a researcher just performed a run of a pilot test and after a certain time, he observed that the population reacted to it reducing its depressive symptoms. Nevertheless, the text says that his experience is limited because he doesn't have and there is a blanc space. The thing here is that the drug seems to have a reaction in the population but he doesn't have a control group that didn't take the pill to see if the pill is effective.
