2020-03-30-Homework-2

95%-confidence intervals for language test score

讀取資料

library(MASS)
dta <- MASS::nlschools[,c(1,2,3)]
str(dta)

## 'data.frame':    2287 obs. of  3 variables:
##  $ lang : int  46 45 33 46 20 30 30 57 36 36 ...
##  $ IQ   : num  15 14.5 9.5 11 8 9.5 9.5 13 9.5 11 ...
##  $ class: Factor w/ 133 levels "180","280","1082",..: 1 1 1 1 1 1 1 1 1 1 ...

依照class切割資料

dta.1 <- split(dta, dta$class)

找出平均數、前後2.5%(題目的範例數字應是IQ_mean)

language_lb <- lapply(dta.1, function(x) quantile(x$lang, 2.5 / 100))
language_ub <- lapply(dta.1, function(x) quantile(x$lang, 97.5 / 100))
IQ_mean <- lapply(dta.1, function(x) round(mean(x$IQ), 3))
class <- unique(dta[,3])

合併資料

dta.2 <- cbind(IQ_mean, cbind(language_lb, language_ub))
dta.bind <- cbind(class, dta.2)
rownames(dta.bind) <- c(1:133)

檢視尾端資料

tail(dta.bind, 3)

##     class IQ_mean language_lb language_ub
## 131 131   11.273  31.25       47.75      
## 132 132   10.55   12.125      50.425     
## 133 133   10.643  21          38.25