The plural of anecdote is anecdotes - not data. -unknown
In ecology, to test a hypothesis we go out and collect data. Most often we need to collect lots of data because the signal is not strong and we need lots of data to account for the messiness that is ecology. So it goes.
Medicine is no different. Because of the differences in age, diet, lifestyles, and genetics we respond differently to medicines. So we need to collect lots of data and do many experiments. The strongest inference we should be able to make and thus have the highest confidence in conclusions based upon many many observations. The observations should be objective and not be open to interpretation to either the researcher or the subject. What I call scientific evidence is a study based on many samples and the data is objectively collected.
The testimonial is the antithesis to science. The person is the "experiment" and they're giving their own interpretation of outcomes so are entirely subjective. I have found that chiropractors often use testimonials to attract business. I'm not sure why. To demonstrate I Googled chiropractors in the Wilkes-Barre area and picked the first one and there it was - testimonials. The next practice with a web-site also had testimonials with a link to a video that is a testimonial to chiropractic in general.
I'm not saying there isn't scientific evidence for chiropractic care - but that should be what people look for when seeking care.