Lesson 2: Visualizing Data

• Frequency table

Something | Frequency
India     | 10
China     | 14
England   | 100

• Relative frequency == proportion
  • Defined as: frequency / total
  • India = 10 / 124 == 0.08
  • Always >= 0 and <= 1
• Percent = proportion * 100
• Histogram
  • Interval/bin/bucket
    • Grouping things like ages: 0 - 19, 20 - 39, 40 - 59
  • Frequency is always y-axis
  • Variable is on x-axis

• Bar graph
  • Different from histogram, each variable is a distinct value
  • x-axis is sometimes categorical rather than numerical/quantitative
• Normal distributions
  • "Peaks in the middle"
• Skewed distributions
  • Peaks toward left or right