Variables and Hypothesis

Variable What is it? change being tested – 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. –W–What are the variables? temperature of water time it takes an egg to cook

Types of Variables Independent/Manipulated Variable (IV): deliberately changed in order to test it – 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): usually a measured change or visually observed change – changes as a result of the independent variable: usually a measured change or visually observed change

Example The more you water the grass, the taller it will grow. – IV 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 DV results to the CV results.

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)

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)51020 DV = Rows (time to assemble puzzle in minutes) 1051 Students of different ages are given the same puzzle to assemble. The puzzle assembly time is measured.

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

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?