Key to assignment 4

1.(a) >truehist(...., ymax=0.5,....)
      Some of you didn't use ymax, and produced `half' pictures.

  (b) x<-seq(-4,4,.01)
      lines(x,dnorm(x)) #default is line type 1
      lines(x, dt(x,5), lty=2)
      legend(-4,0.5, c("normal","t_5"), lty=c(1,2))

  (c) Some constructed qqplot of `change' with a random sample from t_5.
      You have to compare distribution of `change' with `theoretical' t_5.
      
      >qqplot( qt(seq(0,1,.01),5), change, plot=T )

  (d) Well, the data were generated from t_5.


2.(a) Population mean 5 implies rate 0.2 (= 1/5)
      >expon<-rexp(200, 0.2)

  (b) >boxplot(..)
      >stem(...)

  (c) >sample(..., replace=T)

  (d) Depends. For small dataset, stem-and-leaf gives more information.