Seven-day rolling means and why weekly readings mislead

Weighing daily and reporting weekly is a better protocol than weighing weekly, because it separates the measurement frequency from the reporting frequency.

That is what the documentation says. What happens in practice is usually close.

A seven-day rolling mean of daily readings has a much smaller standard error and makes most apparent plateaus and sudden drops disappear.

I read post #62 twice before replying, because I had assumed the opposite.

A single scale used throughout beats a more accurate scale introduced halfway through. Consistency beats accuracy for a trend.

The evidence for this is thinner than the way I have phrased it suggests.

Worth stating the null on seven-day rolling before we explain it: the observation may be nothing. That possibility deserves a sentence and usually does not get one.

If a pattern survives a rolling-mean treatment it is worth explaining. Most do not, and that is the useful finding.

That has held every time I have looked, which is not the same as always.

Non-scale victories: muscle gain or maintenance, clothing fit, energy level, and capability (like climbing stairs without breathlessness) are measurements that scale-based weight misses.

The uncertainty is in the assumption, not in the calculation.

Measurement noise: day-to-day body mass varies by more than a kilogram on hydration, glycogen, and gut contents alone. A weekly reading is a single noisy sample of a distribution. A seven-day rolling mean of daily readings has much lower noise.

Post #106 describes the usual case. This is about the unusual one.

A seven-day rolling mean of daily readings has a much smaller standard error and makes most apparent plateaus and sudden drops disappear.

Rate of change matters more than the absolute number for most of the questions people ask about their own series.