Equation 12 · Part 1 · Forty Million Clicks Through One Uneven Door
Symbol sigma_Y
What this part means
the outcome’s population standard deviation.
Its job in the formula
sigm is a part of this expression. Its role is fixed by the surrounding article and by the operations shown in the formula.
Full expression→Symbol sigma_Y→Article meaning
Where the article explains it
where is the “data defect correlation” between selection and outcome across the full population, f = n/N is the sampling fraction, and is the outcome’s population standard deviation.
The passage around this formula
where is the “data defect correlation” between selection and outcome across the full population, f = n/N is the sampling fraction, and is the outcome’s population standard deviation. The identity’s uncomfortable lesson for any self-selected big-data project is that the error term does not shrink as n grows unless f grows with it — and for a national population sampled through a viral website, f stays vanishingly small no…
Learn the underlying idea
A subscript is a label attached below a symbol. It often selects a time step, component, category, or member of a sequence.
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Sources cited in the surrounding passage
These citations provide research context; check each source for the exact claim it supports.