4. Probability

4.2 forms of variability

• in statistics context, data is obtained by selecting sample from the target population, then measuring the quantities of interest for the subject that belongs to the target.

• variability of the data can be summarized by aid of:

  • frequency table
  • relative frequency table
  • cumulative relative frequency table

• the variability of data can be graphically displayed using:

  • bar plot.
  • histogram
  • box plot

• the variability of data can be numerically displayed using:

  • mean
  • median
  • sample variance
  • sample standard deviation

• forms of variability:

  • variability of data (discussed above, related to the sample itself).
  • the population variability.
  • the variability of random variable.

• the aim of the variability of random variable is to:

  1. model the notion of randomness in measurements.
  2. model the uncertainty of outcome of measurements.