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Overview of basic concepts in Statistics and Probability - SAMSI

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Scal<strong>in</strong>g <strong>and</strong> limits<br />

<strong>Overview</strong> <strong>of</strong><br />

<strong>basic</strong> <strong>concepts</strong><br />

<strong>in</strong> <strong>Statistics</strong><br />

<strong>and</strong><br />

<strong>Probability</strong><br />

Avanti<br />

Athreya<br />

Prelim<strong>in</strong>aries<br />

Important<br />

distributions,<br />

scal<strong>in</strong>g laws,<br />

<strong>and</strong> the CLT<br />

Parametric<br />

estimation <strong>and</strong><br />

hypothesis<br />

test<strong>in</strong>g<br />

The strong law <strong>of</strong> large numbers (SLLN) says that the sample<br />

mean Sn<br />

n<br />

converges to the true mean with probability one.<br />

The Central Limit Theorem (CLT), on the other h<strong>and</strong>, says<br />

that if we scale differently—i.e. look at S n / √ n, we get a<br />

non-determ<strong>in</strong>istic limit—<strong>in</strong>deed, the sequence <strong>of</strong> r<strong>and</strong>om<br />

variables looks approximately like a Gaussian r<strong>and</strong>om variable.<br />

These results illustrate the importance <strong>of</strong> scal<strong>in</strong>g—how we<br />

<strong>in</strong>troduce large (or small) parameters <strong>and</strong> take limits.

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