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Why does the sample mean converge to 50 in this example?

The sample mean converges to 50 because 50 is the expected value E(X)E(X) of the random variable XX (number of heads in 100 fair-coin tosses). According to the law of large numbers, as the number of trials nn approaches infinity, the sample mean X‾n\overline{X}_n approaches the expected value.

Conditions

  • The coin is fair.
  • XX counts heads after 100 tosses.
  • nn approaches infinity.

Reasoning, step by step

  1. Calculate the expected value E(X)=100⋅0.5=50E(X) = 100 \cdot 0.5 = 50.
  2. Apply the law of large numbers: X‾n→E(X)\overline{X}_n \to E(X) as n→∞n \to \infty.
  3. Conclude that X‾n→50\overline{X}_n \to 50.

Example

The on-screen statement reads X‾n→50\overline{X}_n \to 50 as n→∞n \to \infty.

Common misconceptions

  • Believing that the sample mean will exactly equal 50 for any finite nn; it only approaches 50 in the limit.

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