Linear Combinations, Parameter Estimation, and Applied Probabilistic Modeling

Linear Combinations, Parameter Estimation, and Applied Probabilistic Modeling

12 marks

The heights, in metres, of female and male students in a particular school follow normal distributions with the following data.

Mean Height (metres)

Variance (metres\(^{2}\))

Female

\(1.6\)

\(0.04\)

Male

\(\mu \)

\({{\sigma }^{2}}\)

It is known that \(20\%\) of the males are shorter than \(1.6\) m, while \(75\%\) of them are below \(1.8\) m. Show that \(\mu \) and \(\sigma \) are \(1.71\) m and \(0.132\) m respectively.

Find the probability that

  1. The heights of two randomly selected female students both exceed \(1.55\) m.[2]
  2. The total height of two randomly selected female students is more than \(3\) m. [3]
  3. A randomly selected male student is taller than a randomly selected female student by at least \(20\) cm.[3]

A random sample of \(20\) female students is chosen. Find the probability that at least \(15\) of these female students are shorter than \(1.7\) m.[4]

Solution:

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Answer:\(\mu\approx1.71\) m, \(\sigma\approx0.132\) m (shown). (i) \(0.358\) (ii) \(0.760\) (iii) \(0.355\) using unrounded parameters; \(0.354\) using the displayed rounded parameters. Final sample probability: \(0.384\).

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