2.3

• Measure of Dispersion


  The difference between the actual value and the average value
• Range


  • The simplest and easiest way to determine measure of dispersion
  • The difference of the highest value (HV) and lowest value (LV) in the data set
• Range


  • Easy to compute
  • Easy to understand
  • Can be distorted by a single extreme value
  • Only two values are used in the calculation
• Calculating Range


  1. Determine the HV and LV in the data set

  2. Solve for the range using the formula: Range = HV - LV
• Calculating Range


  • The daily rates of a sample of 8 employees at GMS Inc. are P550, P420, P560, P500, P700, P670, P860, P480. The range is P440.
• Standard Deviation (SD)


  • One of the most widely used measures of dispersion
  • Calculated as the square root of variance
  • Provides a good indication of volatility
  • Measures how widely values are dispersed from the average
• Variance


  The mathematical expectation of the average squared deviations from the mean
• Calculating Range, Variance and Standard Deviation

  • Example 1: The scores of 5 randomly selected students in STAT 101 in a 30-point quiz are 27, 20, 15, 12, 21.
  • Example 2: The scores of 4 members of the Mathematics club are 33, 35, 39, and 29.