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Overview of basic concepts in Statistics and Probability - SAMSI

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Estimat<strong>in</strong>g the sample mean<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 />

Suppose we take a r<strong>and</strong>om sample <strong>of</strong> women <strong>and</strong> measure their<br />

heights.<br />

Some assumptions:<br />

1 Each woman’s height is a normal r<strong>and</strong>om variable X i with<br />

mean µ <strong>and</strong> variance σ;<br />

2 The variables X i are <strong>in</strong>dependent.<br />

The strong law <strong>of</strong> large numbers says that with probability one,<br />

as n → ∞,<br />

∑ n<br />

i<br />

X i<br />

ˆµ = → µ<br />

n<br />

∑ n<br />

i X<br />

So ˆµ = i<br />

n<br />

is a good estimator for µ.

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