Using standardization to find probabilities

Using standardization to find probabilities

IB Year 6 | Grade 12

If \(X \sim N(k, k^2)\), find

    1. \(\mathrm{P}(X > 0)\)
    2. \(\mathrm{P}\left(X < \frac{k}{2}\right)\)
  1. The constant \(a\) such that \(\mathrm{P}(|X - k| < ak) = 0.9\).

Solution:

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Answer:For \(k>0\): (a)(i) \(0.841\), (ii) \(0.309\) (b) \(a\approx1.64\). For \(k<0\): (a)(i) \(0.159\), (ii) \(0.691\) (b) \(a\approx-1.64\). The non-degenerate normal model requires \(k\ne0\).

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