a) Given that "\\mu=15 \\ years, \\sigma=2.3\\ years"
"X\\sim N(\\mu, \\sigma^2)"
"X\\sim(15, 2.3^2)"
b) "X\\sim N(\\mu, \\sigma^2)." Then
"\\mu=15 \\ years, \\sigma=2.3\\ years"
"=P(Z<{16.1-15 \\over 2.3})-P(Z<{13.9-15 \\over 2.3})\\approx"
"\\approx0.683768-0.316232\\approx0.3675"
"P(13.9<X<16.1)=0.3675"
c)
"P(Z<{\\mu+\\delta-\\mu \\over \\sigma})-P(Z<{\\mu-\\delta-\\mu \\over \\sigma})=0.2"
"P(Z<{\\delta \\over \\sigma})-P(Z<-{\\delta \\over \\sigma})=0.2"
"P(Z<-{\\delta \\over \\sigma})={1-0.2 \\over 2}=0.4"
"-{\\delta \\over \\sigma}\\approx-0.253348"
"\\delta\\approx2.3\\cdot0.253348=0.5827004"
"\\mu-\\delta\\approx15-0.5827004\\approx14.4173"
"\\mu+\\delta\\approx15+0.5827004\\approx15.5827"
"Low:14.4173 \\ years"
"High:15.5827\\ years"
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