The effects of the z-score transformation on measures of relative erectile response strength: A re-appraisal

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Abstract

In studies of stimulus control of sexual arousal, some researchers transform raw data to z-scores. Earls, Quinsey and Castonguay [Archives of Sexual Behavior, 16, 493–500 (1987)] have argued that the proportion of variance due to stimulus presentations was greater in z-scores than in the raw data or in a percent score. We present analyses of sexual arousal data that show that z-score transformations may distort the information inherent in the raw data and may increase random error. In addition, we present Monte Carlo analyses indicating that the z-score transformation compromises the estimates of Type I error, and, depending on specific circumstances, sometimes increases and sometimes decreases the power of the statistical test. Transformation of raw data to percent of full erection does not distort the information in the raw data, does not compromise the data analyses and, therefore, is the preferred transformation.

References (18)

  • H.E. Barbaree et al.

    Deviant sexual arousal in rapists

    Behaviour Research and Therapy

    (1979)
  • D.J. Baxter et al.

    Sexual responses to consenting and forced sex in a large sample of rapists and nonrapists

    Behaviour Research and Therapy

    (1986)
  • K. Freund

    Diagnosing homo- or heterosexuality and erotic age-preference by means of a psychophysiological test

    Behaviour Research and Therapy

    (1967)
  • G.G. Abel et al.

    The components of rapist's sexual arousal

    Archives of General Psychiatry

    (1977)
  • J.H.J. Bancroft et al.

    A single transducer for measuring penile erection with comment on its use in the treatment of sexual deviates

    Behaviour Research and Therapy

    (1966)
  • H.E. Barbaree et al.

    Erectile responses among heterosexual child molesters, father-daughter incest offenders, and matched non-offenders: five distinct age preference profil

    Canadian Journal of Behavioural Science

    (1989)
  • H.E. Barbaree et al.

    The reliability of the rape index in a sample of rapists and nonrapists

    Violence and Victims

    (1989)
  • A.C. Bebbington

    A simple method of drawing a sample without replacement

    Applied Statistics

    (1975)
  • P.R. Davidson et al.

    The reliability of the Rape Index: a rapist sample

    Behavioral Assessment

    (1985)
There are more references available in the full text version of this article.

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