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15 Cards in this Set

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Define Experimental variable
An aspect of an experiment which changes during the course of the experiment
Define Control (of an experiment)
The variable or part of the experiment to which all others can be
compared
Define Blind studies
Experiments in which the participants do not know whether or not they are a
part of the control group
Define Double-blind studies
Experiments in which neither the participants nor the people analyzing
the results know who is in the control group
When is an experimental variable good
An experimental variable is good when you are using it to learn something from the experiment.
When should an experimental variable be reduced or eliminated?
When it affects the results of the experiment but you do not learn anything from it.
A consumer laboratory decides to test the effectiveness of different laundry detergents.Five white shirts are stained with grass stains and put into five different washers. In one washer, no laundry detergent is used. In the other four washers, four different types of laundry detergent are used, one type in each washer. Water from the same source is used to fill each washer. The washers are then turned on, and once they are finished, the shirts are examined by eye to see which is the cleanest. What is the control for this experiment?
x
A consumer laboratory decides to test the effectiveness of different laundry detergents. Five white shirts are stained with grass stains and put into five different washers. In one washer, no laundry detergent is used. In the other four washers, four different types of laundry detergent are used, one type in each washer. Water from the same source is used to fill each washer. The washers are then turned on, and once they are finished, the shirts are examined by eye to see which is the cleanest. What is the experimental variable that will be used to learn something from the experiment?
The experimental variable that can be used to learn something from the experiment is the type
of detergent used.
A consumer laboratory decides to test the effectiveness of different laundry detergents. Five white shirts are stained with grass stains and put into five different washers. In one washer, no laundry detergent is used. In the other four washers, four different types of laundry detergent are used, one type in each washer. Water from the same source is used to fill each washer. The washers are then turned on, and once they are finished, the shirts are examined by eye to see which is the cleanest. What are the experimental variables that need to be reduced or eliminated?
There are at least four unwanted experimental variables. First, the washers are different. It is
possible that some clean clothes better than others. This affects the results of the experiment,
because you will not know whether the difference in cleanliness is due to the washer or the
detergent. In addition, the water can be at different temperatures, which will affect the outcome.
Also, the shirts are different. Some fabrics are easier to clean than others. Finally, the amount of
grass stain will be different in each shirt, because there is no way to stain shirts equally.
A consumer laboratory decides to test the effectiveness of different laundry detergents. What could be done to reduce or eliminate the unwanted experimental variables?
The experimental variable of the washers can be reduced by making sure all washers are the
same brand and model, and by making sure they are all relatively new. This will reduce the
difference between the effectiveness of each washer. You can reduce the differences in water
temperature by monitoring the temperature of the water as it enters each washer and making
adjustments to keep the temperature the same. The experimental variable of the shirts can be
reduced by making sure they are all from the same manufacturer, the same style, and the same
fabric. That way, they are as close to identical as possible. Finally, the experimental variable of
the amount of stain can be reduced by examining each stain carefully and trying to make sure
they are as identical as possible.
Why can a carefully-placed needle float on water, even though the needle is more dense than the water?
The needle floats because of surface tension.
What does soap do to the surface of water?
Soap reduces the surface tension of water.
A student tries to float a needle on water. He succeeds, but only after several attempts. He then tries to float the same needle on another liquid. Although the needle sinks when dropped in the liquid, it is much easier to lay the needle on the surface of this liquid and make it float than it was to get the needle to float on water. Compare the surface tension of this liquid to that of
water.
The liquid must have a larger surface tension than water, because the needle floats more easily on this liquid than on water.
subjective
- not impartial: based on somebody's opinions or feelings rather than on facts or evidence
objective
impartial, information based upon measurable facts or evidence