R: Mizon-Richard test for dose-response models

mr.test {drc} | R Documentation

## Mizon-Richard test for dose-response models

### Description

The function provides a lack-of-fit test for the mean structure based on the Mizon-Richard test as compared to a specific alternative model.

### Usage

    mr.test(object1, object2, object, x, var.equal = TRUE, component = 1)

### Arguments

`object1` | object of class 'drc' (null model).
`object2` | object of class 'drc' (alternative model).
`object` | object of class 'drc' (fitted model under alternative).
`x` | numeric vector of dose values.
`var.equal` | logical indicating whether or not equal variances can be assumed across doses.
`component` | numeric vector specifying the component(s) in the parameter vector to use in the test.

### Details

The function provides a p-value indicating whether or not the mean structure is appropriate.

The test is applicable even in cases where data are non-normal or exhibit variance heterogeneity.

### Value

A p-value for test of the null hypothesis that the chosen mean structure is appropriate as compared to the alternative mean structure provided (see Ritz and Martinussen (2011) for a detailed explanation).

### Note

This functionality is still experimental: Currently, the null and alternative models are hardcoded! In the future the function will be working for null and alternative models specified by the user.

### Author(s)

Christian Ritz

### References

Ritz, C and Martinussen, T. (2011) Lack-of-fit tests for assessing mean structures for continuous dose-response data, Environmental and Ecological Statistics, 18, 349–366

### See Also

See also `modelFit` for details on the related lack-of-fit test against an ANOVA model.

### Examples

    ## Fitting log-logistic and Weibull models
    ## The Weibull model is the alternative
    etmotc.m1<-drm(rgr1~dose1, data=etmotc[1:15,], fct=LL.4())
    etmotc.m2 <- update(etmotc.m1, fct=W1.4())

    ## Fitting the fitted model (using the alternative model)
    etmotc.m3 <- drm(fitted(etmotc.m1)~dose1, data=etmotc[1:15,], fct=W1.4())

    ## Handling missing values
    xVec <- etmotc[1:15,]$dose1
    xVec[1:8] <- 1e-10  # avoiding 0's

    ## Obtaining the Mizon-Richard test
    mr.test(etmotc.m1, etmotc.m2, etmotc.m3, xVec, var.equal = FALSE)

[Package drc version 3.0-1 Index]