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
: 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.
firstname.lastname@example.org 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.
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
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.
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 10.45.84.252