Differences

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--- degrees_of_freedom [2019/09/24 12:43] – hkimscil
+++ degrees_of_freedom [2020/04/11 18:06] – hkimscil
@@ Line 30: / Line 30: @@
 |   | Xi  | ds  | ds<sup>2</sup>  |
-|   | 2  | -1  | 1  |
+| 1 | 2  | -1  | 1  |
-|   | 3  | 0  | 0  |
+| 2 | 3  | 0  | 0  |
-|   | 2  | -1  | 1  |
+| 3 | 2  | -1  | 1  |
-|   | 4  | 1  | 1  |
+| 4 | 4  | 1  | 1  |
-|   | 5  | 2  | 4  |
+| 5 | 5  | 2  | 4  |
-|   | 5  | 2  | 4  |
+| 6 | 5  | 2  | 4  |
-|   | 2  | -1  | 1  |
+| 7 | 2  | -1  | 1  |
-|   | 2  | -1  | 1  |
+| 8 | 2  | -1  | 1  |
-|   | 4  | 1  | 1  |
+| 9 | 4  | 1  | 1  |
-|   | 1  | -2  | 4  |
+| 10 | 1  | -2  | 4  |
 | sum  | 30  | 0  | 18  |
 | N  | 10  |   |   |
@@ Line 69: / Line 69: @@
   * sd = 1.258306
   * n-1 대신 n을 사용했을 때는 0.9437293
 <code>
-k <- c(2, 3, 2, 4, 5, 5, 2, 2, 4, 1)
+############
-set.seed(1024)
+set.seed(1010)
-ks <- sample(k, 4)
+n.pop <- 20
-mean(ks)
+k <- sample(1:20, n.pop, replace = T)
-sd(ks)
+k.mean <- mean(k)
-(sd(ks)*3)/4
+k.pvar <- var(k)*((n.pop-1)/n.pop) ## population var(k)
-#########
+k.mean
-mean(k)
+k.pvar
-sd(k)
+############
+n.samp <- 3
+ks <- sample(k, n.samp)
+ks
+ks.mean <- mean(ks)
+ks.var <- var(ks)
+ks.pvar <- var(ks)*((n.samp-1)/n.samp)
-</code>
+ks.mean ## sample mean
+ks.var ## sample variance
-<code>
+ks.pvar ## sample variance as population
-> k <- c(2, 3, 2, 4, 5, 5, 2, 2, 4, 1)
+k.mean ## population mean
-> k
+k.pvar ## population variance as pop
- [1] 2 3 2 4 5 5 2 2 4 1
+############
->
-> set.seed(1024)
-> ks <- sample(k, 4)
-> mean(ks)
-[1] 2.25
-> sd(ks)
-[1] 1.258306
-> (sd(ks)*3)/4
-[1] 0.9437293
->
-> sd(k)
-[1] 1.414214
->
-> mean(k)
-[1] 3
 </code>