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Using the TINspire invNorm function

Using the TINspire invNorm function

IB Year 6 | Grade 12

Example 2 (Calculating unknown value of random variable given probability using Ti Nspire invNorm function)

Given \(X \sim N(50, 100)\), find

  1. \(a\) if \(P(X < a) = 0.925\)
  2. \(b\) if \(P(X > b) = 0.113\)
  3. the range of values of \(c\) if \(P(X > c) < 0.123\)
  4. \(d\) if \(P(|X - 50| \geq d) = 0.125\)

Solution:

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Answer:(i) \(a=64.4\). (ii) \(b=62.1\). (iii) \(c>\operatorname{invNorm}(0.877,50,10)\), whose cutoff is approximately \(61.6011988\). (iv) \(d=15.3\). Values in (i), (ii) and (iv) are to 3 significant figures.

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