Dependency of Anxiety on Stress

Description

Stress and anxiety among nonclinical women in Townsville, Queensland, Australia.

Usage

data("StressAnxiety", package = "betareg")

Format

A data frame containing 166 observations on 2 variables.

stress

score, linearly transformed to the open unit interval (see below).

anxiety

score, linearly transformed to the open unit interval (see below).

Details

Both variables were assess on the Depression Anxiety Stress Scales, ranging from 0 to 42. Smithson and Verkuilen (2006) transformed these to the open unit interval (without providing details about this transformation).

Source

Example 2 from Smithson and Verkuilen (2006) supplements.

References

Smithson, M., and Verkuilen, J. (2006). A Better Lemon Squeezer? Maximum-Likelihood Regression with Beta-Distributed Dependent Variables. Psychological Methods, 11(7), 54–71.

See Also

betareg, MockJurors, ReadingSkills

Examples

data("StressAnxiety", package = "betareg")
StressAnxiety <- StressAnxiety[order(StressAnxiety$stress),]

## Smithson & Verkuilen (2006, Table 4)
sa_null <- betareg(anxiety ~ 1 | 1,
  data = StressAnxiety, hessian = TRUE)
sa_stress <- betareg(anxiety ~ stress | stress,
  data = StressAnxiety, hessian = TRUE)
summary(sa_null)
summary(sa_stress)
AIC(sa_null, sa_stress)
1 - as.vector(logLik(sa_null)/logLik(sa_stress))

## visualization
attach(StressAnxiety)
plot(jitter(anxiety) ~ jitter(stress),
  xlab = "Stress", ylab = "Anxiety",
  xlim = c(0, 1), ylim = c(0, 1))
lines(lowess(anxiety ~ stress))
lines(fitted(sa_stress) ~ stress, lty = 2)
lines(fitted(lm(anxiety ~ stress)) ~ stress, lty = 3)
legend("topleft", c("lowess", "betareg", "lm"), lty = 1:3, bty = "n")
detach(StressAnxiety)

## see demo("SmithsonVerkuilen2006", package = "betareg") for more details