Steps to making a histogram
When a histogram has uneven bins, the height does not equal the frequency. However, histograms don’t always have even bins. For example, if you are plotting magnitudes of earthquakes and your bins are 3-5, 5-7 and 7-9, each bin is spaced two numbers apart and so the height of the bar would equal the frequency. The height of a bar in a histogram indicates frequency (counts) only if the bin widths are evenly spaced. The frequency is calculated by multiplying the width of the bin by the height. Unlike a bar chart, the area of a bar in a histogram represents the frequency, not the height. What does the height of a bar in a histogram represent? For example, if you are making a histogram of ages and your bins include 40-42 and 42-44, a participant who is 42 years old should be placed in the 42-44 bin. Most graphs you’ll create in elementary statistics will have about 5 to 7 bins.Īnother rule of thumb for bins is that if a value falls into two bins, place it in the upper bin. Fewer than 5 bins and your graph will have little (if any) meaning. Any more than 20 bins and your graph will be hard to read. There are no set rules about how many bins you can have, but the rule of thumb is 5-20 bins. Normally, you choose the range that best fits your data. A histogram displays the same categorical variables in “bins”.Ī bin shows how many data points are within a range (an interval). A bar graph charts actual counts against categories The height of the bar indicates the number of items in that category. Histograms are similar to bar charts they are a way to display counts of data.