In a study of the periodical cicada (Magicicada septendecim), researchers measured the hind tibia lengths of the shed skins of 110 individuals. Results for males and females are shown in the accompanying table.

(a) Use a t test to investigate the association of tibia length on gender in this species. Use the 5% significance level.
(b) Given the preceding data, if you were told the tibia length of an individual of this species, could you make a fairly confident prediction of its sex? Why or why not?
(c) Repeat the t test of part (a), assuming that the means and standard deviations were as given in the table, but that they were based on only one-tenth as many individuals (6 males and 5 females).

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Tibia length (um) Group n Males 60 Females 5080.44 3.52 Mean SID 78.42 2.87