Let "X=" the number of pieces of candy: "X\\sim B(n,p)."
Then
"{\\sigma_x^2 \\over \\mu_x}={np(1-p) \\over np}=1-p"
Given that "\\mu_x=6, \\sigma=2.3"
"n={\\mu_x \\over p}\\approx51"
"P(X=x)=\\binom{n}{x}p^x(1-p)^{n-x}"
"P(X=9)\\approx\\binom{51}{9}({0.71 \\over 6})^9({5.29 \\over 6})^{51-9}\\approx0.0698"
The probability that your kid sister will hit up a house giving out 9 pieces of candy is "0.0698"
Comments
Leave a comment