title: The mathematical formula of the intravaginal ejaculation latency time (IELT) distribution of lifelong premature ejaculation differs from the IELT distribution formula of men in the general male population.
abstract: OBJECTIVE
  To find the most accurate mathematical description of the intravaginal ejaculation latency time (IELT) distribution in the general male population.
  
  
  METHODS
  We compared the fitness of various well-known mathematical distributions with the IELT distribution of two previously published stopwatch studies of the Caucasian general male population and a stopwatch study of Dutch Caucasian men with lifelong premature ejaculation (PE). The accuracy of fitness is expressed by the Goodness of Fit (GOF). The smaller the GOF, the more accurate is the fitness.
  
  
  RESULTS
  The 3 IELT distributions are gamma distributions, but the IELT distribution of lifelong PE is another gamma distribution than the IELT distribution of men in the general male population. The Lognormal distribution of the gamma distributions most accurately fits the IELT distribution of 965 men in the general population, with a GOF of 0.057. The Gumbel Max distribution most accurately fits the IELT distribution of 110 men with lifelong PE with a GOF of 0.179. There are more men with lifelong PE ejaculating within 30 and 60 seconds than can be extrapolated from the probability density curve of the Lognormal IELT distribution of men in the general population.
  
  
  CONCLUSIONS
  Men with lifelong PE have a distinct IELT distribution, e.g., a Gumbel Max IELT distribution, that can only be retrieved from the general male population Lognormal IELT distribution when thousands of men would participate in a IELT stopwatch study. The mathematical formula of the Lognormal IELT distribution is useful for epidemiological research of the IELT.
authors.affiliation: Department of Central Hospital Pharmacy, Viecuri Hospital, Venlo, The Netherlands.; Division of Pharmacology, Utrecht Institute of Pharmaceutical Sciences, Utrecht University, Utrecht, The Netherlands.
authors.forename: Paddy K C
authors.initials: PK
authors.lastname: Janssen
authors.affiliation: Division of Pharmacology, Utrecht Institute of Pharmaceutical Sciences, Utrecht University, Utrecht, The Netherlands.; Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, PA, USA.; Private Practice of Psychiatry and Neurosexology, Amstelveen, The Netherlands.
authors.forename: Marcel D
authors.initials: MD
authors.lastname: Waldinger
mesh_terms: D003075:Coitus / Q000502:physiology; D003627:Data Interpretation, Statistical; D004542:Ejaculation / Q000502:physiology*; D006801:Humans; D008297:Male; D008954:Models, Biological; D061686:Premature Ejaculation / Q000503:physiopathology*; D012016:Reference Values; D013997:Time Factors
keywords: Goodness of Fit; Gumbel Max distribution; Intravaginal ejaculation latency time; Lognormal distribution; Premature ejaculation