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Field Experiments and Lab Experiments

Discussion of the distribution and abundance of living organisms and how these properties are affected by interactions between the organisms and their environment

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Field Experiments and Lab Experiments

Postby mmmmmm » Wed Oct 08, 2008 4:51 am

Would you use a large number of replicates in a field or lab experiment? I think you would need a large number of replicates in both..but which would be larger?
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Postby mith » Wed Oct 08, 2008 9:45 am

think about variable control
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Postby canalon » Wed Oct 08, 2008 3:19 pm

Think about costs.... The sad reality of life in a lab.
Patrick

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any proof. (Ashley Montague)
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Postby AstusAleator » Wed Oct 08, 2008 10:15 pm

Field experiments are limited by the environment. Sometimes replication is impossible because of the impacts of the data collection.

Lab experiments are limited by budgets, but are set up better for replication.
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Re: Field Experiments and Lab Experiments

Postby mmmmmm » Thu Oct 09, 2008 12:42 am

AstusAleator wrote:Field experiments are limited by the environment. Sometimes replication is impossible because of the impacts of the data collection.

Lab experiments are limited by budgets, but are set up better for replication.


what would be an example of this? i dont understand
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Postby AstusAleator » Thu Oct 09, 2008 1:57 am

In the field, sometimes in order to collect the data, you end up significantly impacting the area such that if you attempted to replicate the data-collection you would get a different result. Furthermore, if you are studying a very sensitive site (endangered habitat for example) you may not be allowed back for a second go-around because the study might adversely impact the species of concern.
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Re:

Postby mmmmmm » Thu Oct 09, 2008 2:15 am

AstusAleator wrote:In the field, sometimes in order to collect the data, you end up significantly impacting the area such that if you attempted to replicate the data-collection you would get a different result. Furthermore, if you are studying a very sensitive site (endangered habitat for example) you may not be allowed back for a second go-around because the study might adversely impact the species of concern.

ah i see, thanks.

one more question...when designing an experiment what determines the size of the plots?
would it be the range of conditions that an organism normally lives in?
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Postby AstusAleator » Thu Oct 09, 2008 2:35 am

Well I already addressed this question to a degree in the other thread you started.

It depends on what you're studying, the size/density of the specie(s), the size/scale of the habitat/environment.

The density of the data and the size of the overall area being studied are probably the two major factors. The purpose of your plot is to include enough data as to be statistically significant when used to make inferences about the greater area.

So if you have a very large area to study, and the specimens are spaced far apart, then you will need a large plot in order to get enough specimens.

An example of this would be:
Imagine a forest of 1 square mile with a tree spacing of 1 tree per 50 square meters. If your objective is to determine the total number of trees in the forest, you would not want to construct a 20 square meter plot. You would probably want a 500 square meter plot. Furthermore, you would probably make more than one plot, in order to get a reliable average.

If you have a very large area, and a high density of specimens, then you can use a smaller plot, but you will probably need to make more plots in the overall area.

Is this making sense?

If you have a small area, and a large spacing between speciments, you will need a large plot.

If you have a small area and small spacing (high density) between specimens, you can use a small plot.

So I guess what I'm saying is: The density (spacing) of the specimens being measured determines the size of the plot, and the overall area being studied determines the number of plots to be measured.
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Re:

Postby mmmmmm » Thu Oct 09, 2008 2:40 am

AstusAleator wrote:Well I already addressed this question to a degree in the other thread you started.

It depends on what you're studying, the size/density of the specie(s), the size/scale of the habitat/environment.

The density of the data and the size of the overall area being studied are probably the two major factors. The purpose of your plot is to include enough data as to be statistically significant when used to make inferences about the greater area.

So if you have a very large area to study, and the specimens are spaced far apart, then you will need a large plot in order to get enough specimens.

An example of this would be:
Imagine a forest of 1 square mile with a tree spacing of 1 tree per 50 square meters. If your objective is to determine the total number of trees in the forest, you would not want to construct a 20 square meter plot. You would probably want a 500 square meter plot. Furthermore, you would probably make more than one plot, in order to get a reliable average.

If you have a very large area, and a high density of specimens, then you can use a smaller plot, but you will probably need to make more plots in the overall area.

Is this making sense?

If you have a small area, and a large spacing between speciments, you will need a large plot.

If you have a small area and small spacing (high density) between specimens, you can use a small plot.

So I guess what I'm saying is: The density (spacing) of the specimens being measured determines the size of the plot, and the overall area being studied determines the number of plots to be measured.

ok i get it..thanks for all the help man :D
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Postby AstusAleator » Thu Oct 09, 2008 2:45 am

No prob. Most people on this forum are pretty helpful if you ask the right questions and try not to sound like you're just cutting and pasting your homework ;)
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