Frequency Distribution and Data Generator

Authors:  Mike Pilant and Bob Hall, Texas A&M University

With this set of applets, instructors can easily and quickly demonstrate difficult to grasp concepts like the Central Limit Theroem.  In addition, students can generate sample data that conforms to user-defined population parameters.  The sample data then can be cut and pasted into other applets (i.e., correlation and regression) for further analysis.

Frequency Distribution and Data Generator Instructions:

  • Click "Reset Pop" first, to initialize distribution, before generating data!
  • Click the "Properties" button to bring up a dialog box where you can
    1. Set the minimum and maximum ranges
    2. Set the number of points, precision and number of classes (intervals).
      Note.  The mean, standard deviation, skewness, and kurtosis of the population distribution are shown in the upper right text area.  The mean, standard deviation, skewness, and kurtosis of the sample distribution are shown to the left of the population statistics.
  • Click the "Options" button to bring up a dialog box where you can
    1. Show the first, second and third quartiles of the sample (shown in green).
    2. Show the mean (vertical black line) and blue lines one or two standard deviations away from the mean (for the sample).
  • The default population distribution is uniform (constant).
  • To change the shape of the distribution, click or drag the mouse above the interval bars to set the height of the bars.  Individual bars may also be moved up or down to "tweek" the shape of the distribution.
  • Click "Write Data" to write data into textarea in right.
  • Click "Read Data" to read data from textarea in right.
  • Click "Reset Sample" to generate new data, without changing the distribution.
  • Click "Sort" to sort sample.  (Clicking it again reverses order.)
    Note: Frequency Distribution is shown in red, and the actual probability distribution curve of the data generated overlaid in blue on top of the histogram.  The statistics of the input histogram are inherited by the output histogram, but the actual statistics of the generated data will differ slightly from the input distribution.

This applet can be used to generate data on [0,1] with presecribed mean, standard deviation, skewness and kurtosis.  You can cut and past the data in the scrolling window to another application such as Excel or SPSS.  [In unix click 3 or 4 times in a row in the scrolling data window, in Windows highlight the data and use ctrl-c to copy]