Chapter 2 Notes

©2009 by S. Gramlich

Definitions and Describing Data (Visually)

! = Important Note

! These Notes are not meant to replace Reading. Read Chapter first.

2-2

Frequency Table = lists counts of # data points for each class (called frequency = f)

Sample Size = n = sum of all f (formula n = Σf)

Σ = Greek uppercase Sigma = add up all the values

! Frequency tables will differ depending upon how many classes are initially chosen.

using StatCrunch: Stat - Tables -Frequency - Select Column - Calculate

Relative Frequency Table = lists relative frequency for each class (found by taking f/n for each class)

f/n = f divided by n

Cumulative Frequency Table = lists cumulative frequency for each class (found by adding the previous f iteratively)

2-3

Histogram = bar graph with class boundaries as horizontal axis and f as vertical axis

! Again Histograms will differ depending upon how many classes initially chosen

using StatCrunch: Graphics - Histogram - Select Column - Create Graph

2-4

Frequency Polygon = connect midpoints on bars of histogram

Will show you 1 of 3 basic shapes or Distributions (from section 3-2):

Normal (0 skewness) = bell shaped and symmetric, hump in middle

Skewed Right = tapered to Right, hump to Left

Skewed Left = tapered to Left, hump to Right