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Conduct Monte Carlo based power analysis using the path diagram interface

Once can conduct power analysis using Monte Carlo based method by drawing a path diagram with population parameters. An example is given in the figure below:

Rules to draw the path diagram


  • : Observed variables.
  • : Latent variables / factors
  • : Mean / intercept
  • : Skewness/kurtosis
  • : Missing data
  • : One-headed arrows for regression paths/factor loadings
  • : Double-headed arrows for variances / covariances


  • Click or or to draw the shape directly.
  • To draw , first select one of the above three shapes and then click the button on the left panel.
  • To draw , first select or , and then click button on the left panel.
  • To draw paths between two shapes
    • Method 1: Click or , then drag your mouse from the start variable to the end variable while pressing the left button of your mouse.
    • Method 2: Click the start variable, then click the arrow path, and then the end variable.
  • Adjust the diagram. Click any shape to highlight it, then move it around.
  • Copy the diagram. First select the shapes by clicking the shapes while holding the “Ctrl” key on your keyboard. Then, click the button to paste.
    • While holing the “Ctrl” key, one can drag a selection window by pressing the right button of the mouse to select multiple shapes.

Rules to specify the population parameters

  • A number such as 1, 0.5, and -2, on the path will be used as population parameters to generate data from the model and the path will be estimated as free parameters in Monte Carlo simulation.
  • To fix a path in the estimation, use @. For example, @1 will be fixed at 1.
  • A path can be provided a name.
    • For example, a?0.5 means the parameter values is 0.5, the parameter name is a, and the path needs to be estimated.
    • a@0.5 means the parameter values is 0.5, the parameter name is a, and the path will be fixed at 0.5 when estimating the model.
  • To specify the skewness and kurtosis for an observed variables, using the path from to . Two numbers separated by “;” are used with first one denoting the skewness and the second one denoting the kurtosis.
  • Default parameters
    • By default, the unspecified variances will be given the value 1 and the unspecified covariance will be given the value 0.
    • The unspecified regression/loading paths will be given a value 0.
    • The unspecified mean/intercept will be givens a value 0.

Conduct the power analysis

Required input

  • Sample size: an integer number for sample size
  • Significance level: 0.05 typically
  • MC replications: How many Monte Carlo replications are used to estimate power. 1000 typically.
  • Power parameters: Parameters other than specified in the diagram. For example, one can get the power for an indirect effect a*b. To get it, specify ab := a*b. Notice that “:=” is used to define a new parameter. Each line provides one such parameter.
  • Notes: put a note for the analysis.

Required input

  • To save the current path diagram, click the button
  • To open an older path diagram, click the button
  • To run the power analysis, click the button
  • To see the output of the power analysis, click the button
  • To download the path diagram as a SVG figure, click the button
  • To draw a new path diagram, click the button
manual/diagram_based_power_analysis.txt · Last modified: 2015/04/28 13:38 by