Day of week seasonality
What it shows
The average daily price change (%) for each day of the week separately over the selected window (1–3 years). Each bar is the plain arithmetic mean of the daily returns falling on that weekday, and the whiskers show the 95% confidence interval of that mean. A historical tendency, not a forecast.
How to read it
Look for bars clearly away from zero, with short whiskers on one side of zero and both badges (FDR-significant + Stable). A bar without badges, or with whiskers through zero, is a curiosity. Remember: this describes the past, nothing here says the pattern will repeat.
Parameters
- Mean change (%)
- The mean of daily returns on that weekday. A green bar = a historically positive mean, red = negative.
- Whiskers / 95% CI
- Whiskers are the 95% confidence interval of the mean: a realistic range for the true value. A narrow interval = a more confident reading.
- Positive reading: The whole interval on one side of zero: a clear tendency across the data window.
- Negative reading: Whiskers crossing zero: the interval contains 0, so it may just as well be noise.
- n (sample size)
- How many historical days back the group. A small n (the “low sample” badge) = a result too noisy to take seriously.
- FDR-significant
- The green badge: the result passed the multiple-comparison correction (Benjamini–Hochberg). Without it, with ~30 tests per profile, a few “significant” results are pure chance.
- Stable over time (walk-forward)
- The stability badge: the effect keeps the same direction in both the earlier and the later half of the window. “Unstable” = the tendency may have already faded.
Example
Monday shows +0.31% with n=104, whiskers +0.05%…+0.57% and both badges: Mondays in this window were, on average, mildly positive historically. Thursday at −0.05% with whiskers through zero and no badges is noise.