Designing a Scientific Test

A test is where a scientist gathers data.

In a comparison test, everything you do to one experimental group must be exactly the same as you do to the other group (control group).The one different factor

is called the variable.

In our tests, we want to collect measureable results

QUESTION: Does adding earthworms to a potted plant make it grow taller than a regular potted plant?

Control GroupRegular Potted

Plant

Experimental GroupPotted

Plant withEarthworms

Variable

Constantssame size pot

same soil

same amount of water

same sunlight

All of the other factors, which are the same for both groups, are called the constants.

Controlled Experiments Vocabulary

Controlled Experiment:

an experiment where the scientist compares the thing they want to test to something they already know about

control group:

the part of the experiment that you know about and can use to compare to the thing you want to investigate

experimental group:

the part of the experiment that has the thing you want to investigate

c.g.

v.

e.g.+ =

generally the thing that you are curious about investigating

Controlled Experiments, cont.

variable:

the one thing that is different between the control group and the experimental group

constants:

the things in your experiment that you keep exactly the samethe only thing in an experiment that is different between the control group and the experimental group is the variable

the variable is usually part of the experimental group

Controlled Experiment Examples

I began to think that my plants would grow bigger if I used fertilizer. Fertilizer is supposed to give plants more nutrients so it should help them to grow.

Question: Will plants fertilized with Frank’s Fabulous Fertilizer grow bigger than a regular plant?

c.g.

Regular Plant

e.g.

Regular Plant with Frank’ Fabulous Fertilizer

+v.

F.F. Fertilizer =

Controlled Experiment Examples

I do not like moldy bread. My regular bread gets moldy in 5 days. I want to find a bread that does not get moldy so quickly.

Question: Will whole wheat bread get moldy faster than my regular bread?

c.g.

Regular Bread

e.g.

Whole Wheat Bread+v.

type of bread

=

Controlled Experiment Examples

I am so hot and thirsty! I want a home-made popsicle, and soon! Should I put sugar in the flavored water to make it freeze faster?

Question: Does sugar water freeze faster than just plain water?

c.g.

Plain Water

e.g.

Plain Water with Sugar added+v.

Sugar =

Controlled Experiment Examples

I want some apple, but not a whole one. What would happen if I just took one bite from one?

Question: Does an apple with one bite taken out rot faster than a whole apple?

c.g.

Whole Apple

e.g.

Apple with Bite Taken Out+v.

One Bite! =