A CLT tail probability

MediumStatistics~4m

Per-trade P&L is i.i.d. from a skewed, non-Normal distribution with mean $50 and standard deviation $10. Over a day you make n=100n=100 independent trades. Using the central limit theorem, estimate the probability that the average P&L per trade exceeds $52. Give a decimal to three places. (Use Φ(2)=0.9772\Phi(2)=0.9772.)

Show hints (2)+
  1. The CLT makes the sample mean Normal - use SE =σ/n=1=\sigma/\sqrt n=1, not σ\sigma.
  2. z=(52−50)/1=2z=(52-50)/1=2, then P(Z>2)=1−Φ(2)P(Z>2)=1-\Phi(2).

Answer

Reveal answer →

0.023 (± 0.002)

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