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Fetal Implants in Mice Utero

Keywords: underdispersion


In an experiment where pregnant mice were exposed to the herbicide 2,4,5-T (the active component in Agent Orange), the number of fetal implants in utero were recorded. The data give the frequency distribution of implants at each of seven dose levels measured in mg/kg of body weight.

On days 6-14 after mating, pregnant dams were dosed by gavage with one of the doses of 2,4,5-T. Prior to giving birth, the dams were sacrificed and the number of viable, dead and reabsorbed foetuses in the uterus of the dam were determined. The data here gives the number of surviving viable implants. An outcome of zero implants cannot be distinguished from a non-pregnant outcome so any zero implant outcomes were excluded.

Variable Descriptions

Dose Dose of 2,4,5-T in mg/kg/day
Implants Number of surviving implants
Frequency Number of mice with that number of implants


Data file (tab-delimited text)


Holson, J.F., Gaines, T.B., Nelson, C.J., LaBorde, J.B., Gaylor, D.W., Sheehan, D.M. and Young, J.F. (1992). Developmental toxicity of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T): I. Multireplicated dose-response studies in four inbred strains and one outbred stock of mice. Fundamental and Applied Toxicology 19, 286-297.

Faddy, M. J., and Bosch, R. J. (1999). Likelihood-based modeling and analysis of data underdispersed relative to the Poisson distribution. Biometrics 57, 620-624.


The counts are underdispersed and left skew relative to the Poisson distribution.


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