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July 15, 2024, 09:10:55 pm

Author Topic: Experimental prac questions  (Read 1406 times)  Share 

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sillysmile

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Experimental prac questions
« on: March 21, 2010, 08:42:11 pm »
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Okay... so what exactly is(are) the control(s) of an experiment?  :-\

I'm a little confused with this.. from what i can gather it seems that
they are the variable(s), in an experiment that remain constant.. or do not have the independant variable manipulating them.
Are the controls the same as the controlled variable/group?
Also could a possible improvement for experimental design be, more experiments?
One other unrelated question, where is amylase found in plants and why? :-\

Thanks for the help :)
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TrueLight

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Re: Experimental prac questions
« Reply #1 on: March 21, 2010, 11:06:01 pm »
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wiki is your friend

'Positive and negative control

Many experiments are designed to include a negative control and a positive control, which are the simplest forms of controls.[1]

Positive controls confirm that the procedure is competent in observing the effect (therefore minimizing false negatives). Negative controls confirm that the procedure is not observing an unrelated effect (therefore minimizing false positives). A positive control is a procedure that is very similar to the actual experimental test, but which is known from previous experience to give a result that is hypothesized to occur in the treatment group (positive result). A negative control is known to give a negative result. The positive control confirms that the basic conditions of the experiment were able to produce a positive result, even if none of the actual experimental samples produce a positive result. The negative control demonstrates the base-line result obtained when a test does not produce a measurable positive result; often the value of the negative control is treated as a "background" value to be subtracted from the test sample results, or be used as the "100%" value against which the test sample results are weighed.

For example, in an enzyme assay to measure the amount of an enzyme in a set of extracts, a positive control would be an assay where you add some of the purified enzyme, and a negative control would be where you do not add any extract. The positive control should give a large amount of enzyme activity, while the negative control should give very low to no activity.

If both the treatment group and the negative control produce the result, it can be inferred that another variable acted on the experiment and the data is discarded. Similarly, if the positive control fails, we know there was something wrong with our procedure so we discard any results and begin again. If both controls behave correctly, we can confidently accept the results of the experiment as the effect of the desired variable.'

http://en.wikipedia.org/wiki/Scientific_control


well repeating experiments would help confirm results ...
improve experimental design.. i dunno youll have to think of any other methods that would make it more reliable..

read through that the first few lines tell you in the intro about amylase... or just wiki lol
http://www.pnas.org/content/89/16/7526.full.pdf
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