If you want to measure the effect of magnets
on plants, you are thinking about two very
important things: controls and sample size.
Controls allow us to be fairly sure that
differences are due to the factor we're trying
to measure, in this case, magnets. Just having
several plants (a large sample size) is
important, but how you treat the plants is
critical in a fair, valid experiment. For
example, you wouldn't want to put all your
magnet plants in one place and all your controls
in another, because the light, temperature, or
something else might be different. You want
several plants that you treat exactly the same
except for having a magnet nearby. A really
good control would be to have non-magnetized
steel in place of magnets for the controls.
You might use 6-10 plants in each group.
More is always better, but you may not have
enough space or magnets. I don't know which
plant would be better, but I would choose plants
that grow quickly and aren't too delicate.
If you are growing plants outside, weather
will definitely make a difference. Even
indoors, plant will be influenced by light
coming in windows, temperature differences in
different areas of the room, and other
Finding out whether there is an effect is
part of the fun of the experiment. Remember not
to let your hopes for a difference influence how
you measure any difference. Think about what
might be good to measure. Plant height? Number
sprouted? Whether it grows in a certain
direction? Number of leaves? There are a lot of
choices. You can record more than one thing.
Start thinking now about how you will show your
results at the end. It may help you design a
I majored in biology. I studied animals
mostly, but good experimental design is the same
in any branch of science.
Goodluck with your experiment.
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