A classic problem of term definition from the NYT (somewhat older article):
A notable study in 2005 showed that a year after surgery, 97 percent of patients were able to achieve an erection adequate for intercourse. But last month, researchers from George Washington University and New York University reviewed interim data from their own study showing that fewer than half of the men who had surgery felt their sex lives had returned to normal within a year.
So which of the studies is right? Surprisingly, they both are.
Basically, the first number hinges on whether the patient occasionally acheives an erection “adequate for intercourse”. The article goes on to say that this definition is pretty inadequate from the patient’s viewpoint:
“That definition is misleading,” said Dr. Jason D. Engel, director of the urologic robotic surgery program at the George Washington University Hospital. “It doesn’t mean it was good intercourse, and it doesn’t even mean your penis was hard. That man is going to say, ‘I’m impotent.’ But in the surgeon’s eyes, that man had an erection adequate for intercourse.”
The better question for men is whether they can have sex when they want to, with or without drugs like Viagra. In a recent series of patients, Dr. Engel found that after a year 47 percent of men who had robotic prostatectomy were able to have regular sex.
Although he could cite statistics to give men a more hopeful view, he said that did not help the patient.
What we stress in the statistical literacy course is that such faulty definitions are not wrong — just ill-suited to the questions they are trying to answer. A man who asked this question before surgery is likely asking a question for which definition #1 is clearly unsuited.