i need a controlled experiment example?

Question

A controlled experiment is one where you subject your hypothisies to a seris of tests while controlling many variables but i need an example

Answer 1

The important thing to do is to identify every variable that you think might affect your results. Suppose your hypothesis is that a plant will grow best with some critical amount of watering, and will not grow as well with more or less water than this critical amount. You might identify the following as other factors that would affect plant growth: soil content, sunlight, air quality. If you set up several plants to receive different amounts of water, you must keep these other factors the same. The plants should be potted in soil from the same source, and they should be placed very close together to maintain sunlight and air quality. In addition, the water for the plants should be taken from the same source to ensure that only the quantity (i.e., not the quality) of water affects the results.

Sometimes, if a controlled experiment provides unexpected results, it becomes possible to identify other variables that should have been controlled. For example, suppose that your results appear to show that a certain amount of water is optimal and more or less water leads to less growth, except that one of the more-watered plants grew much less than even the plants that were watered more than it. This might cause you to realize that this plant was placed above a radiator vent, and that you failed to control temperature, which turned out to also be a significant variable.

Answer 2

A controlled experiment involves making sure that a control exists - that is something that is not subject to the experimental conditions to prove the efficacy of the experimental methodology. For example: If a drug were being tested say for cancer therapy - a "control group" would exist who were told they were taking the drug but actually might be given a sugar pill or "placebo" - the people getting the actual drug are then compared to those who only got the placebo to see if the real drug actually helped the condition. If there was no control group then there would be no way to separate what happens when the pill is taken from spontaneous remissions etc. Sometimes people who take the placebo also claim to have benefits that are ascribed to the original drug - and this is what is called "the placebo effect" - and can sometimes indeed render changes in circumstances in someone in a control group - the effect is not that well understood - but thought to be due to thr role that the mind and belief has in response to a condition.

Answer 3

How about buoyancy changes of an object in water relative to the salt content of the water?

(See the "salt content gage" on thermometers designed to float in aquariums.)
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