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Feb/Mar 2023 p52 q6
3225
In a different cycling event, the times can also be modelled by a normal distribution. 23% of the cyclists have times less than 36 minutes and 10% of the cyclists have times greater than 54 minutes.
Find estimates for the mean and standard deviation of this distribution.
Solution
Let the mean be \(\mu\) and the standard deviation be \(\sigma\).
For the time less than 36 minutes, 23% corresponds to a \(z\)-score of approximately \(-0.739\). Thus,
\(z_1 = \frac{36 - \mu}{\sigma} = -0.739\)
For the time greater than 54 minutes, 10% corresponds to a \(z\)-score of approximately \(1.282\). Thus,