Identifying Variables

Let’s Review…. 6 steps of the Scientific Method? Identify the Problem Research Hypothesis Experiment Data Analysis Conclusion

Today’s Focus Step 4- EXPERIMENT

Designing a valid experiment is easy- once you identify your variables!

A variable is something that changes.

What variables affect the taste of a chocolate chip cookie? Example: What variables affect the taste of a chocolate chip cookie?

Cookie Variables Recipe Amount of ingredients Brands of ingredients used Baking time Oven temperature Type of oven Type of cookie sheet

1 variable in an experiment! You can only test 1 variable in an experiment! Once you decide what you want to test, you must determine how to manage everything else.

Independent Variable Dependent Variable “Constant” Variables 3 Types of Variables Independent Variable Dependent Variable “Constant” Variables (aka Constants)

the variable that is changed on purpose by the experimenter independent variable the variable that is changed on purpose by the experimenter aka cause, stimulus, reason, manipulated variable, what you are testing etc. This is the ‘’if” part of a hypothesis.

the variable that responds dependent variable the variable that responds aka effect(s), result(s), responding variable, etc. This is the ‘’then” part of a hypothesis.

constants all other variables that are NOT allowed to change during the experiment

3 Concepts for Valid Experiments Control Group Treatment Group Repeated Trials

control group the group (standard) to which everything is compared (this group doesn’t actually do the experiment!!)

the group(s) being tested with the independent variable treatment group the group(s) being tested with the independent variable *This group actually does the experiment!*

the number of times the experiment is repeated repeated trials the number of times the experiment is repeated The more times you repeat the experiment, the more VALID your results are.

helps you design an experiment. IVCDV The chart helps you design an experiment.

Problem: how does fertilizer affect plant growth??

These are the fertilizer amounts varied by the experimenter. iv constants dv fertilizer The variable (factor) that you will change is the independent variable. 0 drops These are the fertilizer amounts varied by the experimenter. 2 drops 4 drops 6 drops

iv constants dv fertilizer plant growth 0 drops The variable (factor) resulting from the independent variable is the dependent variable. 2 drops 4 drops 6 drops

iv constants dv fertilizer amt. of water plant growth type of soil 0 drops These are the factors that must NOT change during experimentation. They must remain constant. amt. of soil 2 drops type of plant 4 drops type of planter 6 drops size of planter type of light location

6 drops fertilizer 4 drops fertilizer 2 drops fertilizer no fertilizer

EXPERIMENTAL GROUP CONTROL 2 drops fertilizer 4 drops fertilizer What is this called? What are these called? CONTROL EXPERIMENTAL GROUP no fertilizer

What are these called? CONSTANTS

dependent variable What is this called? The plant growth that you observe here can be called . . .  the results (of adding fertilizer)  the response (to adding fertilizer) dependent variable  the effects (of adding fertilizer) 2 4 6

Type of soil becomes the IV. What do you do if you want to test the type of soil instead of fertilizer? iv dv constants plant growth fertilizer amt. of water type of plant type of planter size of planter amt. of soil type of light location type of soil type of soil fertilizer Type of soil becomes the IV. Fertilizer becomes a constant.

In the following two slides, identify the independent variable constants dependent variable.

Evaluate the experimental design in the next two slides.

Let’s Practice ID’ing Variables All types…not specific types just yet

HW: V.P. 1 You are ID’ing specific types of variables (IV, C, DV)