dodPwr: Power of the Degree-of-Difference (DOD) method In sensR: Thurstonian Models for Sensory Discrimination

Description

Computes the power of the Degree-of-Difference (DOD) method by simulation

Usage

 1 2 3 4 5 6 7 dodPwr(d.primeA, d.prime0=0, ncat = 4, sample.size, nsim = 1e3, alpha = 0.05, method.tau=c("LR.max", "equi.prob", "se.min", "user.defined"), statistic=c("likelihood", "Wilcoxon", "Pearson", "Wald"), alternative = c("difference", "similarity", "two.sided", "less", "greater"), tau=NULL, ...)

Arguments

 d.primeA the value of d-prime under the alternative hypothesis; non-negative numerical scalar. d.prime0 the value of d-prime under the null hypothesis. ncat the number of response categories in the DOD model sample.size the sample size in each simulation for each of the same-pairs and different pairs. Can be a single scalar value or a 2-vector. nsim the number of simulations. alpha the significance level. method.tau the method with which to choose the boundary parameters - see dodSim for details on the methods. statistic the statistic to be used for hypothesis testing. alternative the nature of the alternative hypothesis in the hypothesis/significance test for d-prime. Note that "greater" is an alias for "difference" and "less" is an alias for "similarity". tau if method.tau = "user.defined" a vector of boundary parameters in the DOD model, otherwise not used. ... parsed on to wilcox.test when appropriate.

Value

The simulation based estimate of the power with the following attributes:

 se(power) the estimated standard error of the estimated power. This is based on the formula sqrt(pow * (1 - pow) / n), where pow is the estimated power and n is the number of simulations used to estimate the power. n.used the number of simulations used to estimate the power. This is usually equal to nsim, but can sometimes be smaller than nsim due to non-convergences to which the Wald test is especially prone.

Author(s)

Rune Haubo B Christensen

References

Ennis, J.M. and R.H.B. Christensen (2014) A Thurstonian comparison of the tetrad and degree of difference tests. Food Quality and Preference, in press.