The data for this project is in data frame Pseudoscorpions, from package abd: require(abd)
Pseudoscorpions: Experiment or Observational Study?
The data for this project is in data frame Pseudoscorpions, from package abd:
require(abd)
data(Pseudoscorpions)
View(Pseudoscorpions)
help(Pseudoscorpions)
From the text Analysis of Biological Data, by Michael C. Whitlock and Dolph Schluter:
Pseudoscorpions of the species Chordylochernes scorpioides live in tropical forests where they ride on the backs of harlequin beetles to reach rotting figs where they feed. Females of the species are promiscuous and mate with multiple males over short lifetimes. It is unclear what advantages there are for a female to mate multiple times, because the males don't help to care for her young, and mating just once provides all the sperm she needs to fertilize her eggs.
One possible advantage is that the sperm of some males is genetically incompatible with a given female and, by mating multiple times, a female increases the chances of mating with at least one male whose sperm is compatible with her. To investigate this idea, Newcomer et al. (1999) recorded the number of successful broods by female pseudoscorpions randomly assigned to one of two treatments. One group of females was each mated to two different males (DM), whereas females in the other group were each mated twice to the same male (SM). By mating each female twice, the same amount of sperm was provided in both treatments, but the DM females received genetically more diverse sperm than the SM females.
The Pseudoscorpions data frame gives the results of this study.
From the above description, it appears that the investigators were interested in the following Research Question:
On average, do female pseudoscorpions who mate with two males produce a larger number of successful broods than do female pseudoscorpions who mate with only one male?
Study the data frame and the above information, and decide which of the following options best explains whether the Pseudoscorpions study was an observational study or a randomized experiment.
- ( ) Observational study, because for a randomized experiment you would have to take a random sample of female Psuedoscorpions from the population, and nowhere in the above information did we learn that this was done.
- ( ) Randomized experiment, because the number of males you mate with is believed to affect the genetic diversity of the sperm you store, which in turn affects your chance of a producing a successful brood.
- ( ) Observational study, because the response variable was successful.broods, and the researchers merely observed how many successful broods each female in the study produced: they did not randomly assign the number of broods to each female.
- ( ) Randomized experiment, because the explanatory variable was treatment, and the researchers randomly assigned the value of this variable to the females in the study: some females were assigned to mate with one male (value "SM") and the others were assigned to mate with two males (value "DM").
Given information:
Given that the investigator is interested to study whether the female pseudoscorpions who mate with two males produce a larger number of successful broods than do female pseudoscorpions who mate with only one male.
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