(タイプIエラーの確率)を指定することに加えて、完全に指定された仮説ペアが必要です。つまり、、、およびが既知である必要があります。(タイプIIエラーの確率)はです。片側を想定してい。R:αμ0μ1σβ1−powerH1:μ1>μ0
> sigma <- 15 # theoretical standard deviation
> mu0 <- 100 # expected value under H0
> mu1 <- 130 # expected value under H1
> alpha <- 0.05 # probability of type I error
# critical value for a level alpha test
> crit <- qnorm(1-alpha, mu0, sigma)
# power: probability for values > critical value under H1
> (pow <- pnorm(crit, mu1, sigma, lower.tail=FALSE))
[1] 0.63876
# probability for type II error: 1 - power
> (beta <- 1-pow)
[1] 0.36124
編集:視覚化
xLims <- c(50, 180)
left <- seq(xLims[1], crit, length.out=100)
right <- seq(crit, xLims[2], length.out=100)
yH0r <- dnorm(right, mu0, sigma)
yH1l <- dnorm(left, mu1, sigma)
yH1r <- dnorm(right, mu1, sigma)
curve(dnorm(x, mu0, sigma), xlim=xLims, lwd=2, col="red", xlab="x", ylab="density",
main="Normal distribution under H0 and H1", ylim=c(0, 0.03), xaxs="i")
curve(dnorm(x, mu1, sigma), lwd=2, col="blue", add=TRUE)
polygon(c(right, rev(right)), c(yH0r, numeric(length(right))), border=NA,
col=rgb(1, 0.3, 0.3, 0.6))
polygon(c(left, rev(left)), c(yH1l, numeric(length(left))), border=NA,
col=rgb(0.3, 0.3, 1, 0.6))
polygon(c(right, rev(right)), c(yH1r, numeric(length(right))), border=NA,
density=5, lty=2, lwd=2, angle=45, col="darkgray")
abline(v=crit, lty=1, lwd=3, col="red")
text(crit+1, 0.03, adj=0, label="critical value")
text(mu0-10, 0.025, adj=1, label="distribution under H0")
text(mu1+10, 0.025, adj=0, label="distribution under H1")
text(crit+8, 0.01, adj=0, label="power", cex=1.3)
text(crit-12, 0.004, expression(beta), cex=1.3)
text(crit+5, 0.0015, expression(alpha), cex=1.3)