There is a difference in each method of getting bodyfat. Even if the method isn't accurate, if he took the measurements at the same sites in the same way, at the same time of day, it would still be a good way to measure his improvements, which was the purpose of getting them anyway.
With calipers there is a particular protocol established for measurement of each site. The problem instructions with the majority of body fat calipers is thay give you an approximate area to measure.
Therein lies the problem. "Garbage in garbage out." The "same sites" are not be measured.
It is the equvalent of weighing yourself on a set of scales in the morning and at night. You are going to get two different reading.
Secondly, to become proficient, it takes practice. A good technician can get a pretty accurate reading even with a cheap set of calipers.
Someone with little to now experience will get consistant inaccurate readings even with Lang calipers.
Third, you can't take you own readings on some of the body parts.
As far as where I got the numbers from, I got them from a textbook titled Fit&Well, one used in one of my college health classes.
I appreciate that information. However, let me restate that 4% is a huge number. Again, that would mean that a 200 lb person would have 8 lbs more fat or 8 pouonds more muscle dependent on the reading.
There is a variance for each method, underwater, electronic, bod-pod, etc. A 4% variance is not very bad.
Again, that would be like a 200 lb man/woman getting a scale and weight either 192 or 208. That is a huge difference.
So, what you are saying is that a 16 lb variance is "not very bad." I'd say it awful.
Skinfold is is the best method to use if one is going to do it at home.
Not bad if you have someone who knows what they are doing.
Also, your not getting a variance in your weight, just in the percentage of bodyfat that you have. So if that 200lb athelite you were talking about got a measurement of 10% +/- 4%, he would either have between 6-14% bodyfat, with the extremes having a less probability of being true. So he would have between 12-28 lbs of bodyfat.
A 12-28 lb variance of body fat is enormous! A 6-14% variance in body fat percentage is insane. There is a night and day difference between those readings.
Your scales are not giving you a percentage of variance for your weight, so I'm not sure if you are just using that as an example of what 4% means, or what. Either way, for the intended purposes, plastic calipers are a cheap and easy way to guage your progress.
The scales are an example. Calipers do basically the same thing in being able to compute in pounds how much fat or muscle you have.
The majority of uneducated individuals using calipers are delusional. The majority come up with unreal number on what their body fat percentage is...meaning they believe their body fat percentage is much lower.
It reminds me of when I would take my blood pressure at times. I'd sit there taking the my reading until I got a number that I liked...lol.
That is what happens with the majority of those uneducated individuals. What you want is a trained technician with who is unbiased...meaning someone who will tell you the truth.