purpose (to find-out)

• phenomenon (group characteristics)
• reason-result (relationship of factotrs)
• economic, social tendencies(, rules)
  • used for predicting future, and helping decision

how

• survey
• experiment
• observation

terms

• unit
  • person
  • state
  • food
  • …
• case (record)
• variable

level of measurement (scale of measure)

• nominal scale : identifying use
• ordinal scale : serial ordering use
• interval scale : scoring use
• ratio scale : ratio use

data

• value’s level
  • qualitaive value
  • quantitative value
• value’s quantity
  • single-meaning value
  • multi-meaning values

data, information repository

• korea
  • kostat
  • kosis
  • korea-index
  • micro data service
  • statstic-geographic information
  • economic information
• global
  • StRD
  • DASL
  • UCI data
  • ksdc
  • usa statistics

center tendency

• mean

  mean(data)
  

• trimmed mean

  mean(data, trim=0.10)
  

• median

  median(data)
  

• mode

  mode(data)
  

dispersion

summary(data)

• variance

• standard deviation

  sd(data)
  

• range

• coefficient of variation

• quartile deviation
  • interquartile range : Q3 - Q1

  IQR(data)
  quantile(data, probs=c(0.25, 0.5, 0.75))  //it's quaNtile, not quaRtile
  

continuous data graph

• histogram

  a = rnorm(200)
  hist(a, col="RED")
  

• stem-and-leaf

  stem(data)
  stem(data, scale=2)
  

• box plot

  boxplot(data)
  

  • five-number-summary -adjacent value

web tool

• statpages
• inteructivate