Create a distribution plot that displays probabilities and data values

In the Distribution Plot dialog box, specify a distribution and parameters, and choose whether to display probabilities or data values.

Select data distribution and parameters

In Distribution, select the distribution for your graph, and then enter values for the parameters.

Binomial

Complete the following steps to enter the parameters for the binomial distribution.
  1. In Number of trials, enter the sample size.
  2. In Event probability, enter a number between 0 and 1 for the probability that the outcome you are interested in occurs. An occurrence is called an "event".

Chi-square

In Degrees of freedom, enter the degrees of freedom to define the chi-square distribution. For more information, go to chi-square distribution.

Discrete

Complete the following steps to enter the parameters for the discrete distribution.

  1. In Values in, enter the column that contains the values to include in the distribution. Usually, values are discrete events or counts that are represented by numeric values.
  2. In Probabilities in, enter the column that contains the probabilities for each value. Probabilities must be between 0 and 1, and must sum to 1.

Exponential

Complete the following steps to enter the parameters for the exponential distribution.
  1. In Scale, enter the scale parameter. The scale parameter equals the mean when the threshold parameter equals 0.
  2. In Threshold, enter the lower bound of the distribution.

F

In Numerator degrees of freedom and Denominator degrees of freedom, enter the numerator and denominator degrees of freedom to define the F-distribution. For more information, go to F-distribution.

Geometric

  1. In Event probability, enter a number between 0 and 1 for the probability that the outcome of interest occurs. An occurrence is called an "event".
  2. From Model, select one of the following to specify the number to model.
    • Total number of trials: The number of trials includes both events and nonevents.
    • Only the number of non-events: Do not include the number of events.

Integer

Complete the following steps to enter the parameters for the integer distribution.
  1. In Minimum value, enter the lower end point of the distribution.
  2. In Maximum value, enter the upper end point of the distribution.

Lognormal

Complete the following steps to enter the parameters for the lognormal distribution.
  1. In Location, enter a value that represents the location of the peak of the related normal distribution.
  2. In Scale, enter a value that represents the spread of the related normal distribution.
  3. In Threshold, enter the lower bound of the distribution.

Normal

Complete the following steps to enter the parameters for the normal distribution.

  1. In Mean, enter the value for the center of the distribution.
  2. In Standard deviation, enter the value for the spread of the distribution.

Poisson

In Mean, enter the average rate of occurrence. For more information, go to Poisson distribution.

t

In Degrees of freedom, enter the degrees of freedom to define the t-distribution. For more information, go to t-distribution.

Uniform

Complete the following steps to enter the parameters for the uniform distribution.

  1. In Lower endpoint, enter the minimum value for the distribution.
  2. In Upper endpoint, enter the maximum value for the distribution.

Weibull

Complete the following steps to enter the parameters for the Weibull distribution.
  1. In Shape parameter, enter the shape parameter to define the Weibull distribution.
  2. In Scale parameter, enter the scale parameters to define the Weibull distribution.
  3. In Threshold parameter, enter the lower bound of the Weibull distribution.

Select the shaded area on the graph

Use these options to shade the area on a plot that represents a value that you enter. Minitab calculates the corresponding x-value or probability and displays both on the plot.

  1. In Shade the area corresponding to the following, select either A specified probability or A specified x value. Minitab calculates the value that is not specified.
  2. Select the area of the plot that you want to shade.
    • Right tail–Shade the area of values that are greater than the probability or x-value that you enter.
    • Left tail–Shade the area of values that are less than the probability or x-value that you enter.
    • Equal tails–Shade the area of values that have equal probabilities.
    • Middle–Shade the area of the values that you entered.
  3. Enter one or more probabilities or x-values that define the endpoints.

Examples of shaded areas

Students must score in the top 10 percent of an entrance exam to be accepted into a certain educational program. The scores are normally distributed with a known mean and standard deviation.

Right tail

Students who have scores of 1621 or greater are accepted into the program.

Left tail

You received a score of 1738 and want to know your percentile. Your score of 1738 is at the 95th percentile.

Equal tails

You want to know the scores at the 2.5th percentile and the 97.5th percentile. At the 2.5th percentile, the score is 583.8 and at the 97.5th percentile, the score is 1838. Approximately 95% of the students have scores that are between 583 and 1838.

Middle

You want to know what percentage of students has scores that are between 800 and 1600. Approximately 79% of the students have scores that are between 800 and 1600.

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