Histogram + Probabilities Charts

The Histogram and Probabilties chart provides combined graphic information about the data distribution, by depicting a histogram of the raw data along with a probability plot. The lower layer of the graph is the histogram, which provides the center, spread, and skewness of the data, while the upper layer is the normal probability plot, which evaluates whether or not the data follow a normal distribution.

Histogram and Probability Chart Example

Construction of the Plot

Histogram Chart

Histogram charts are obtained by splitting the range of data into equal-sized bins, or class intervals (automatically or by user specification). Then for each bin, the number of points from the dataset that fall into each bin are counted. The result is a plot of Frequency (i.e. counts for each bin) on the vertical axis vs. response variable on the horizontal axis. Since the bins created in the histogram are of equal width this type of histogram is sometimes called a bar chart.

Probability Plot

The Probability plot is formed by plotting the cumulative frequency of observations vs. bins value, and then rescaling the Y axis to the Probability scale type. If the data points follow a normal distribution, the plot should appear as a straight line. Otherwise, skewness and variation can be reflected in the plot.

A note regarding the probability scale: This scale represents the inverse of a cumulative Gaussian distribution. Plotting a cumulative Gaussian distribution produces a sigmoidally-shaped curve. This curve, when displayed on a probability scale, will appear as a straight line when the data normally distributed. Since probabilities are expressed as percentages, all values must fall between 0 and 100. The probability scale range is 0.0001 to 99.999.

Histogram and Probability Plot Options

Primary Options

These properties are associated specifically with this plot type:

• bin size
• begin
• end
• distribution curve overlay
• update probability scale to go from 0 to 1 by employing a divide by factor

Basic Options

All of the basic data plot properties of Scatter and Column/Bar plots can be updated for Origin's Histogram + Probabilities chart as well. This includes:

• Line and Symbol Plots:
  • Properties: shape, size, color, drop lines, line connection type, etc.
  • Learn more about Line and Symbol Properties...*
• Column/Bar Plots:
  • Border Properties: style, width, and color
  • Fill Properties: color, pattern
  • Pattern Properties: border style, width, and color; pattern width and color
  • Spacing: between each column/bar
  • Learn more about Column/Bar Properties...*