Too much noise in my data
September 1, 2012 11:33 AM Subscribe
Putting on the math signal: calling the statistics-literate. Trying to change my weight/body composition and track progress in a useful way, but I'm having trouble separating normal daily variation from actual real change.
posted by ctmf to Science & Nature (15 answers total) 2 users marked this as a favorite
After more than 30 years of being the skinny kid, I would like to look more like a normal adult male person. While I don't need to be a ripped men's magazine model, looking good in my clothes for once would be nice. So I'm doing Starting Strength, which I am enjoying, and also concentrating on my diet. I definitely feel better, and think I'm starting to see some improvement in how I look. And I guess that's the important part.
But here's the annoying part. It's not super-important because, like I said, how I feel is the main thing. But, as a curiosity/motivation thing, I'd like to track my progress with data of some sort.
So I'm tracking the weight I'm lifting, obviously, but also my body weight. Problem is, my weight seems to vary so much anyway from day to day, I can't really tell if there is a trend in my weight, or if I just randomly got a few high measurements in a row.
What I've got now is a spreadsheet with my daily measured weight. I'm doing my best to eliminate sources of error, such as using the same scale every time, same time of day, etc., but I'm still looking at a pretty noisy set of data. I'm using a double exponentially-smoothed curve to kind of eyeball it, with the smoothing factors set pretty low, and that looks kind of promisingly up-slope, but when I look at the raw data points, I could also easily convince myself that there has been no change at all, with standard deviation of my points over two pounds. Plus, standard deviation from a simple mean is less than RMS error of my smoothed curve. Is that bad?
So my question is for actual scientific-type people, in two three parts: 1) what would you measure in the first place to track progress, if not body weight, and how would you track it using a simple tool like excel 2) how can I tell (like, use nerdy statistical tests) if my eyeball impression of "looks like it's going up" is actually a real trend or not, and if so, how much is it going up? Or is it just one of those things where the change is going to be too small to see until a long time passes? (I'm only 3 weeks in)
(Yes, I know. You're envious/would love to have my problem/hate me. I'm kind of weary of those jokes, thanks.)