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--- b:r_cookbook:probability [2020/05/01 21:36] – [qt, pt] hkimscil
+++ b:r_cookbook:probability [2025/09/17 08:22] (current) – [Plotting a Density Function] hkimscil
@@ Line 53: / Line 53: @@
 > pnorm(84, mean=72, sd=15.2, lower.tail=FALSE)
 [1] .2149176
+</code>
+<code>
+> qnorm(.5)
+[1] 0
+> qnorm(.975)  # 왼쪽이 .975 면적일 때의 점수
+[1] 1.959964
+> qnorm(.975, lower.tail=F) # 오른쪽 부분이 .975일 때의 점수
+[1] -1.959964
 > qnorm(.2149176, mean=72, sd=15.2, lower.tail=FALSE)
 [1] 84
@@ Line 97: / Line 108: @@
 > qt(c(0.025, 0.975), df=100)
 [1] -1.983972  1.983972
->
 > qt(c(0.025, 0.975), df=400)
 [1] -1.965912  1.965912
@@ Line 298: / Line 309: @@
 </code>
-{{dnorm_x.png|Normal distribution plot}}
+[{{:b:r_cookbook:pasted:20250917-081835.png|Normal distribution plot}}]
 <code>> x <- seq(from=-3, to=+3, length.out=100)
@@ Line 307: / Line 318: @@
 </code>
-{{standard_normal_distribution.png|standard_normal_distribution}}
+[{{:b:r_cookbook:pasted:20250917-081929.png|standard_normal_distribution}}]
-<code>> # The body of the polygon follows the density curve where 1 <= z <= 2
+<code>
-> region.x <- x[1 <= x & x <= 2]
+# The body of the polygon follows the density curve where 1 <= z <= 2
-> region.y <- y[1 <= x & x <= 2]
+region.x <- x[1 <= x & x <= 2]
->
+region.y <- y[1 <= x & x <= 2]
-> # We add initial and final segments, which drop down to the Y axis
-> region.x <- c(region.x[1], region.x, tail(region.x,1))
+# We add initial and final segments, which drop down to the Y axis
-> region.y <- c(          0, region.y,                0)
+region.x <- c(region.x[1], region.x, tail(region.x,1))
-> polygon(region.x, region.y, density=-1, col="red")
+region.y <- c(          0, region.y,                0)
+polygon(region.x, region.y, density=-1, col="red")
 </code>
+[{{:b:r_cookbook:pasted:20250917-082138.png|standard_normal_distribution}}]
-{{standard_normal_distribution_1-2.png|standard_normal_distribution}}