Bayesian IndependentSample Inference: Prior Distribution
You can specify the following prior distribution criteria for your Bayesian IndependentSample Inference:
Note: Many applied researchers may question the need to specify a prior. Reference priors
minimize the concern where the prior is generally overwhelmed as the data increases. When
informative prior information is specified, Bayesian methods can effectively use the information.
The requirement to specify a prior should not be viewed as a deterrent to using Bayesian
analysis.
 Data Variance
 Provides options for defining data variance settings.
 Variance known

When selected, allows you to enter two known group variances. Both values must be > 0.
 Assume equal variance
 Controls whether or not the two group variances are assumed to be equal. By default, it is assumed that group variances are unequal. This setting is ignored when values are entered for the two group variances.
 Assume unequal variance
 Controls whether or not the two group variances are assumed to be unequal. By default, it is assumed that group variances are unequal. This setting is ignored when values are entered for the two group variances.
 Prior on variance
 Specify the prior distribution for the two equal variances.
 Jeffreys
 When selected, a noninformative (objective) prior distribution for a parameter space is used.
 InverseChiSquare
 Specifies the continuous probability distribution of a positivevalued random variable and the
parameters for inverseχ^{2}(ν_{0},σ^{2}_{0}), where ν_{0} >
0 is the degree of freedom, and σ^{2}_{0} > 0 is the scale parameter.
 Degrees of freedom
 Specify a value for the number of values in the final calculation that are free to vary.
 Scale Parameter
 Specify the scale parameter σ^{2}_{0} > 0 for inverseχ^{2}(ν_{0},σ^{2}_{0}). You must enter a single value that is greater than 0. The larger the scale parameter, the more spread out the distribution.
 Prior on mean conditional on variance
 Provides options for specifying the prior distribution for the two group means.Note: The Diffuse and Normal options are available only when the Variance known option is selected.
 Diffuse
 The default setting. Specifies the diffuse prior.
 Normal
 When selected, you must specify location and scale parameters for the defined group means.
 Location Parameter
 Enter a numeric values that specifies the location parameters for the group distributions.
 Scale Parameter
 Specify the scale parameter σ^{2}_{0} > 0 for inverseχ^{2}(ν_{0},σ^{2}_{0}). For each group, you must enter a single value that is greater than 0. The larger the scale parameter, the more spread out the distribution.