Help with a stats word problem...

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joeypeter

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A researcher dissected the retinas of 20 randomly sampled fish belonging to each of two subspecies of guppy in Venezuela. Using a sophisticated laboratory apparatus, the researcher was able to compare the two groups of fish in the wavelengths of visible light to which the cones of the retina were most sensitive.

a) Is this an experimental study or an observational study? why?

b) what are the two variables being associated in this study?

c) which is the explanatory variable and which is the response variable?
 
This exercise is asking you to read the story, review the definitions, and use your knowledge of the English language.

a) Are they conducting experiments or are they observing and recording values?

b) What is the only thing in the story of which there are "two"?

c) What are they trying to measure response in and response to?

Please reply with your thoughts and work so far. Thank you! :D

Eliz.
 
I am in the same stats course as question asker guy and i have been working on the problem, asked many people, lots of smart people and there is a large amount of disagreement. I think that the experiment is observational, my reason being that the researcher is comparing the two fish species and her specialized technique is just to determine between species, not an actual experimental proceedure... am i correct?

-sad struggling stats student
 


Yes, you are correct.

It's an observational study because the researchers are only observing a natural event. They aren't changing anything about the wavelength range of the two sub-species' retinal cones.

One potential reason for confusion is that observational studies are also known as "natural experiements", especially when observing attributes of the natural world.

In an experimental study, researchers subject something to their designed alterations. In other words, they change something, to see what effect is gained.

 
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