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대수정규분포 [2012/07/10 20:03] moonrepeat 새로 만듦 |
대수정규분포 [2021/03/10 21:42] |
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- | ====== 대수정규분포 (Lognormal Distribution) ====== | ||
- | ===== 표기 ===== | ||
- | [[확률변수]] $Y = \ln X$가 [[정규분포]] $N(\mu, \sigma^{2})$을 따를 때 $X$는 [[대수정규분포]]를 따르고 아래와 같이 표기 한다. | ||
- | $$ X \sim LN(\mu , \sigma^{2})$$ | ||
- | ===== 받침 ===== | ||
- | $$ x \in ( \ 0 \ , \ \infty \ ) $$ | ||
- | ===== 확률밀도함수 ===== | ||
- | $$ f(x) = \frac{1}{\sqrt{2 \pi} \ \sigma \cdot x} \exp \left[ - \frac{(\ln x - \mu)^{2}}{2 \sigma^{2}} \right] $$ | ||
- | |||
- | <plot> | ||
- | set title "Lognormal Distribution PDF" | ||
- | set size 1.0 | ||
- | set xrange [0:8] | ||
- | set yrange [0:1.2] | ||
- | set format x "%.1f" | ||
- | set format y "%.2f" | ||
- | set xlabel "x" | ||
- | set ylabel "f(x)" | ||
- | |||
- | f(x,m,s) = (1/(sqrt(2*pi*s)*x))*exp(-((log(x)-m)**2)/(2*s)) | ||
- | |||
- | plot f(x,0,1) title "LN(0,1)", \ | ||
- | f(x,0,4) title "LN(0,4)", \ | ||
- | f(x,0,0.5) title "LN(0,0.5)", \ | ||
- | f(x,1,1) title "LN(1,1)" | ||
- | </plot> | ||
- | ===== 누적분포함수 ===== | ||
- | $$ F(x) = \frac{1}{2} \left[ 1 + \operatorname{erf} \left( \frac{\ln x - \mu}{\sigma \sqrt{2}} \right) \right] $$ | ||
- | |||
- | <plot> | ||
- | set title "Lognormal Distribution CDF" | ||
- | set size 1.0 | ||
- | set xrange [0:8] | ||
- | set yrange [0:1.1] | ||
- | set format x "%.1f" | ||
- | set format y "%.2f" | ||
- | set xlabel "x" | ||
- | set ylabel "F(x)" | ||
- | set key 7,0.3 | ||
- | |||
- | f(x,m,s) = 0.5*(1+erf((log(x)-m)/sqrt(2*s))) | ||
- | |||
- | plot f(x,0,1) title "LN(0,1)", \ | ||
- | f(x,0,4) title "LN(0,4)", \ | ||
- | f(x,0,0.5) title "LN(0,0.5)", \ | ||
- | f(x,1,1) title "LN(1,1)" | ||
- | </plot> | ||
- | ===== 기대값 ===== | ||
- | $$ E(x) = e^{\mu + \sigma^{2}/2} $$ | ||
- | ===== 분산 ===== | ||
- | $$ Var(x) = e^{2 \mu + \sigma^{2}} \ (e^{\sigma^{2}} - 1}) $$ | ||
- | ===== 왜도 ===== | ||
- | $$ \gamma_{1} = \sqrt{e^{\sigma^{2}} - 1} \left( 2 + e^{\sigma^{2}} \right) $$ | ||
- | ===== 첨도 ===== | ||
- | $$ \gamma_{2} = e^{4 \sigma^{2}} + 2 e^{3 \sigma^{2}} + 3 e^{2 \sigma^{2}} - 6 $$ | ||
- | ===== 원적률 ===== | ||
- | $$ \mu'_{1} = e^{\mu + \sigma^{2}/2} $$ | ||
- | |||
- | $$ \mu'_{2} = e^{2 \mu + 2 \sigma^{2}} $$ | ||
- | |||
- | $$ \mu'_{3} = e^{3 \mu + 9 \sigma^{2}/2} $$ | ||
- | |||
- | $$ \mu'_{4} = e^{4 \mu + 8 \sigma^{2}} $$ | ||
- | ===== 중심적률 ===== | ||
- | $$ \mu_{2} = e^{2 \mu + \sigma^{2}} \left( e^{\sigma^{2}} - 1 \right) $$ | ||
- | |||
- | $$ \mu_{3} = e^{3 \mu + 3 \sigma^{2}/2} \left( e^{\sigma^{2}} - 1 \right) \left( e^{\sigma^{2}} + 2 \right) $$ | ||
- | |||
- | $$ \mu_{4} = e^{4 \mu + 2 \sigma^{2}} \left( e^{\sigma^{2}} - 1 \right) \left( e^{4 \sigma^{2}} + 2 e^{3 \sigma^{2}} + 3 e^{2 \sigma^{2}} - 3 \right) $$ | ||
- | |||
- | ---- | ||
- | * [[분포]] | ||
- | * [[정규분포]] |