Potential reasons for mixed results in clinical trials

[Pegcity]

youtube.com/watch?v=ap-eyxo32A(Not working as expected?)

vjneurology.com/video/ua5d2...

[Boscoejean]

What would be your summary of what they are saying in this video? Is it that the symptoms are variable and some things work for some and some things work for others and some just don't work for anyone? The reason I prefer print reports to videos is that you have to sit through a long video to glean about 5 minutes of useful information because they always need to give the whole background on the symptoms because of course the video is being presented with the idea that the person is totally new to diagnosis and may not know a lot about what to expect.