Hermaphrodites are animals that possess the reproductive organs of both sexes. Genetical Research (June 1995) published a study of the mating systems of hermaphroditic snail species. The mating habits of the snails were classified into two groups:
(1) Self-fertilizing (selfing) snails that mate with snails of the same sex and
(2) Cross-fertilizing (out-crossing) snails that mate with snails of the opposite sex. One variable of interest in the study was the effective population size of the snail species. The means and standard deviations of the effective population size for independent random samples of 17 out-crossing snail species and 5 selfing snail species are given in the accompanying table.

a. Compare the mean effective population sizes of the two types of snail species with a 90% confidence interval. Interpret the result.
b. Geneticists are often more interested in comparing the variation in population size of the two types of mating systems. Conduct this analysis for the researcher. Interpret the result.

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Effective Population Size Sample Size Standard Deviation Snail Mating System Mean Outcrossing Selfing 17 5 4,894 4,133 1,932 1,890