designing an A variable is something that changes

designing an

A variable is something that changes.

6 concepts of experimental design independent variable constants control group experimental group repeated trials

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

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

constants all factors which are NOT allowed to change during the experiment

control group the group (standard) to which everything is compared

experimental group the group(s) being tested with the independent variable Each test group has only one factor different from the other test groups: the independent variable.

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

The IVCDV chart is used to design an experiment.

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 Plants with no fertilizer make up the control or control group.

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

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

6 4 2 dr op s s rt i fe dr op no ze r ti li fe rt ili er liz

4 2 L X E dr op s N E E P M I R A T dr op s L 6 s rt i fe dr op O no TR CO N ti li fe r ze r fe rt ili er liz U G O R ze r P ti li What is this called? What are these called?

What are these called? S T N A T S N O C

What is this called? e l the results (of adding fertilizer) ab i the response (to adding fertilizer) r a the effects (of adding fertilizer) v t n e d n e p e d The plant growth that you observe here can be called. . . 0 2 4 6

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

Take 7 minutes to design an experiment using the IVCDV chart to test the strengths of various sunscreen on aliens. 5 spf 10 spf 15 spf 20 spf

Evaluate the experimental design in the next two slides.

forming a

V Chart

iv dv constants fertilizer amt. of water plant growth type of planter ve rb ve type of plant + + amt. of soil rb type of soil size of planter type of light location If fertilizer is added to plants, then plant growth will improve.

V Chart rb ve ve rb + If independent variable + verb, Dependent Variable + Independent Variable then dependent variable + verb. hypothesis