Variables and Hypothesis

Variable What is it? Variable: something that can change in an experiment. Most commonly known as the factor/thing being tested in the experiment.

Example The time it takes to run a kilometer depends on the amount of exercise a person gets. What are the variables? amount of exercise time to run a km ***Must include how each variable is measured or described!!!

Example The higher the temperature of water, the faster an egg will cook. What are the variables? temperature of water time it takes an egg to cook

Types of Variables Independent/Manipulated Variable (IV): variable that is deliberately changed in order to test it (in most lab situations, you are changing this variable on purpose) Dependent/Responding Variable (DV): changes as a result of the manipulated variable: usually a measured change or visually observed change

Example The more you water the grass, the taller it will grow. IV DV amount of water DV height of the grass

Example More bushels of potatoes will be produced if the soil is fertilized more. IV amount of fertilizer DV bushels of potatoes produced

Types of Variables Control Variable (CV): A variable that is NOT changed. It is kept the same throughout and is often the most NORMAL situation. You compare the MV results to the CV results.

Identify and Control the Variable The Control Group is a group whose conditions are not being changed. The Experimental Group is the group whose conditions are being changed.

Students of different ages are given the same puzzle to assemble Students of different ages are given the same puzzle to assemble. The puzzle assembly time is measured. IV age of student DV time it takes to assemble the puzzle CV puzzle (same)

Students of different ages are given the same puzzle to assemble Students of different ages are given the same puzzle to assemble. The puzzle assembly time is measured. Tables: When creating data tables and graphs, the placement of the IV and DV is important. Title: Time to assemble a puzzle based on age IV = Columns (student age in years) 5 10 20 DV = Rows (time to assemble puzzle in minutes) 1

Students of different ages are given the same puzzle to assemble Students of different ages are given the same puzzle to assemble. The puzzle assembly time is measured. Graph X axis IV Y axis DV Time in Minutes Age of Students

Hypothesis Hypothesis possible explanation for a set of observations or an answer to a scientific question. Based on a person’s observations and previous knowledge or experience. Hypotheses must be testable through an investigation.

How to Write a Hypothesis If the independent variable changes then the dependent variable changes . Always write your hypothesis in the third person (no I or you statements).

Practice! Write a hypothesis based on this question: What is the relationship between free seating at lunch and the cleanliness of the tables?

More Practice! What is the relationship between eating candy in science and good behavior?