Experimental Design Practice

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```					                            Experimental Design
How do you plan and conduct an experiment?
Experiment
 It is the scientific way to prove whether your hypothesis is correct or not.
It includes: materials and the procedure- that is what are you doing in the
experiment, how it is set up, and what materials you are using.

There are two set ups to every experiment: the experimental setup with the variable and
controlled setup which is done under normal or ideal conditions.
Variable
It is one of the conditions that may effect the result of your experiment and it is what
you change to determine if your hypothesis is correct or not.
Independent/Manipulated Variable
 The variable that is changed on purpose or varies in an experiment.
There should only be one variable for each experiment.
Example: giving different amounts of water to same type of plant.
Dependent/Respondent Variable –“RESULTS”
 The variable that changes in response to the independent variable.
 How it changes “depends” on the independent variable.
 It is the results that you measure or observe.
Example: growing plants with different amounts of
water(independent variable) you measure how they grew
differently(dependent variable).
Constants/Controlled Variables
 Factors that remain the same throughout the experiment. If factors like temperature,
method of experimenting, etc. are allowed to vary they might affect the results in a
confusing way.
Repeated Trials & Sample Size
 The experiment is repeated at least a few times to collect as many measurements as
is reasonable. Usually take an average of all the data points.
Control Setup
 The experiment where the conditions are not changed but are kept ‘normal,’
‘natural,’ or ‘ideal.’
 It is the standard which the results from the experimental setup are compared with,
to see if the changed variable make a difference.
Experimental Design Practice                                    Name
Period:      Date

Identify:
independent variable–double underline
dependent variable ---circle
constants-(controlled variables)—outline with a rectangle
control experiment--highlight
repeated trials/sample size--underline once

#1.   Ten radish seeds were planted in each of the five pots found around the house
that each contained 2 kg of “Pete’s Potting Soil” and were grown in a greenhouse
where the temperature and humidity and amount of light was kept the same. The pots
were given the following amounts of distilled water each day for 40 days: Pot 1, 50 ml;
Pot 2, 100 ml, Pot 3, 150 ml, Pot 4, 200 ml; Pot 5, 250 ml. Because Pot 3 received the
recommended amount of water, it was used as a control part of the experiment. This
experiment was repeated five times. The height of each plant was measured at the end
of the experiment and represented in a growth chart and line graph.

#2.   Gloria wanted to find out if the color of food would affect whether kindergarten
children would select it for lunch. She put food coloring into 4 identical bowls of
mashed potatoes. The colors were red, green, yellow and blue. She also served a
sample of potatoes that were of normal color. Each sample was served fresh and warm
with a square of butter. Each child was asked to choose a scoop of potatoes from any
of the colors offered. Gloria did this experiment using 100 students of the same age.
She recorded the number of students that chose each color and made a bar graph.

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