IBM® SPSS® Amos™ 28

The tuning parameter affects the covariance matrix of the multivariate normal distribution from which parameter values are sampled. Initially the covariance matrix is obtained by multiplying the tuning parameter by the parameter covariance matrix obtained from the information matrix evaluated at the maximum of the likelihood.

The Adapt button can be used to automatically set the tuning parameter to a reasonable value.

See How the MCMC algorithm works for a description of the role of the tuning parameter in the MCMC algorithm.