Histograms (DP IB Applications & Interpretation (AI)): Revision Note

Histograms

What is a (frequency) histogram?

• A frequency histogram clearly shows the frequency of class intervals

  • The classes will have equal class intervals

  • The frequency will be on the y-axis

  • The bar for a class interval will begin at the lower boundary and end at the upper boundary

• A frequency histogram is similar to a bar chart

  • A bar chart is used for qualitative or discrete data and has gaps between the bars

  • A frequency histogram is used for continuous data and has no gaps between bars

What are (frequency) histograms useful for?

• They show the modal class clearly

• They show the shape of the distribution

  • It is important the class intervals are of equal width

• They can show whether the variable can be modelled by a normal distribution

  • If the shape is symmetrical and bell-shaped