Question

A statistician uses Chebyshev's Theorem to estimate that at least 15 % of a population lies between the values 9 and 20. Use this information to find the values of the population mean, μ , and the population standard deviation σ.

Answer 1

Answer:

\mu = 14.5\\

\sigma = 5.071\\

k = 1.084

Step-by-step explanation:

given that a  statistician uses Chebyshev's Theorem to estimate that at least 15 % of a population lies between the values 9 and 20.

i.e. his findings with respect to probability are

$P(9<x<20) \geq 0.15\\P(|x-14.5|<5.5) \geq 0.15$

Recall Chebyshev's inequality that

$P(|X-\mu |\geq k\sigma )\leq {\frac {1}{k^{2}}}\\P(|X-\mu |\leq k\sigma )\geq 1-{\frac {1}{k^{2}}}$

Comparing with the Ii equation which is appropriate here we find that

$\mu =14.5$

Next what we find is

$k\sigma = 5.5\\1-\frac{1}{k^2} =0.15\\\frac{1}{k^2}=0.85\\k=1.084\\1.084 (\sigma) = 5.5\\\sigma = 5.071$

Thus from the given information we find that

$\mu = 14.5\\\sigma = 5.071\\k = 1.084$