Statistics Tip of the Week: What's the difference between a Bar Chart and a Histogram?

Both Bar Charts and Histograms use the height of bars (rectangles of the same width) to visually depict data. So, they look similar.
 
But, they

1. differ in whether the bars are separated or placed together (contiguous)
2. depict different types of data, and
3. are used for different purposes

 
1. Separated or contiguous

• Bar Charts: separated

• Histograms: contiguous (the example pictured appears to not be contiguous only because the count is zero for the bins 10-19 and 20-29).

 
2. Types of data

• Bar Charts: Counts or Percentages of Nominal (also known as "Categorical") Variables. These Variables have names as their values (e.g. "chocolate", "vanilla", "strawberry"), not numbers.
• Histograms: Counts or Percentages or Probabilities of the number of data points within a Range 

 
3. How Used

• Bar Charts are used to display relative sizes (of the counts of the named values). 
• Histograms are used to display the shape of the Distribution of the data. The Histogram pictured above tells us that the data is roughly Normally Distributed.