The researchers confirmed by examining the females that the males kept with virgin females were indeed reproducing and that those kept with newly insemincated females were not. Is there evidence that the different sex conditions result in significantly different longevities in laboratory male fruit flies? Check the conditions for ANOVA run the test and conclude.
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- Alternative Hypothesis (H1): There is a significant difference in longevity among male fruit flies kept with virgin females and those kept with newly inseminated females. Show more…
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Scientists are interested in whether the energy costs involved in reproduction affect longevity. In this experiment, 125 male fruit flies were divided at random into five sets of 25. In one group, the males were kept by themselves. In two groups, the males were supplied with one or eight receptive virgin female fruit flies per day. In the final two groups, the males were supplied with one or eight unreceptive (pregnant) female fruit flies per day. Other than the number and type of companions, the males were treated identically. The longevity of the flies was observed. Data from Hanley and Shapiro (1994). Companions | Longevity (days) None | 35 37 49 46 63 39 46 56 63 65 56 65 70 63 65 70 77 81 86 70 70 77 77 81 77 1 pregnant | 40 37 44 47 47 47 68 47 54 61 71 75 89 58 59 62 79 96 58 62 70 72 75 96 75 1 virgin | 46 42 65 46 58 42 48 58 50 80 63 65 70 70 72 97 46 56 70 70 72 76 90 76 92 8 pregnant | 21 40 44 54 36 40 56 60 48 53 60 60 65 68 60 81 81 48 48 56 68 75 81 48 68 8 virgin | 16 19 19 32 33 33 30 42 42 33 26 30 40 54 34 34 47 47 42 47 54 54 56 60 44 4. 2!2 factorial among the five treatments. (a) Construct a set of 4 mutually orthogonal contrasts that include a comparison of the control against the other four treatments, and three contrasts that give the usual factorial partitioning among the treatments with at least one ‘‘companion’’. (b) Obtain the ANOVA table with F tests for each contrast, and make appropriate conclusions.
Ameer S.
(c) Actually, the 10,000 larvae in each group came from a series of 50 different runs of the experiment, with 200 larvae in each group for each run. The researchers believe that conditions differ from run to run, and thus it makes sense to treat each run as a case (rather than each fly). In this analysis, we are looking at paired data, and the response variable would be the difference in the number of larvae surviving between the choice group and the no choice group, for each of the 50 runs. The counts (Choice and NoChoice and difference (Choice - NoChoice) in number of surviving larva are stored in MateChoice. Using the single variable of differences, calculate the p-value for testing whether the average difference is greater than 0. [Hint: this is a single quantitative variable, so the corresponding test would be for a single mean.] Round your answer to three decimal places. p-value= (d) Using a significance level of ̑ = 0.05 and the p-value from (c), do we have evidence that the average difference is greater than 0? (e) The experiment being tested in parts (a) - (d) was designed to mimic the experiment from the original study, yet the original study yielded significant results while this study did not. If mate choice really does improve offspring fitness in fruit flies, did the follow-up study being analyzed in parts (a) - (d) make a Type I, Type II, or no error? Type II error No error Type I error (f) If mate choice really does not improve offspring fitness in fruit flies, did the original Nature study make a Type I, Type II, or no error? Type I error Type II error No error
Dominador T.
In some animal species, exposure to males reduces the lifespan of females because of the damage caused by harassment and male seminal fluids. In other species, exposure to other females is more harmful than exposure to males because of resource competition or aggressive interactions between females. Khan et al (2018) tested these effects in the flour beetle Tribolium castaneum, whose females are known to produce toxins called quinones that may affect other individuals. They created groups of beetles that had equal numbers of males and females ("unbiased" sex ratio), more males than females ("male-biased" sex ratio), or more females than males ("female-biased" sex ratio). They measured the number of offspring for each female beetle. The results of their analysis are presented in the ANOVA table below.
David N.
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