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Equation 11 · Part 2 · Forty Million Clicks Through One Uneven Door

Symbol n

f=n/Nf = n/N
nn

What this part means

n is an input to the expression that computes the quantity on the left.

Its job in the formula

n is an input to the expression that computes the quantity on the left.

The passage around this formula

…f = n/N is the sampling fraction, and σY\sigma_Y 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 matter how large n gets. Meng introduced this identity using the 2016 US presidential election’s Cooperative Congressional Election Study data as its worked example, and the…

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Learn the underlying idea

A variable is a named place for a value. Its letter is a local label: x can mean position in one formula and a data point in another.

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Sources cited in the surrounding passage

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