#11 Variables, Controls, Constants #11 Variables, Controls, Constants and Graphing Variablesand Graphing Variables

VariableVariable

Any factors that can change during Any factors that can change during an experiment (it varies).an experiment (it varies).

There are two types There are two types

– – Dependent Dependent

– – IndependentIndependent

Independent variableIndependent variable (A manipulated variable in an (A manipulated variable in an

experiment whose presence determines experiment whose presence determines the change in the dependent variable.)the change in the dependent variable.)

The one that The one that II decide to change or decide to change or determine. determine.

What is being tested outWhat is being tested out

ex: how many skittles, how much waterex: how many skittles, how much water

Place on x-axis.Place on x-axis.

Dependent variableDependent variable (The observed variable in an experiment (The observed variable in an experiment

whose changes are determined by the whose changes are determined by the presence of the independent variables.)presence of the independent variables.)

What you are recording as your What you are recording as your DData.ata.

What is being measured What is being measured ex: work rate, plant heightex: work rate, plant height

Place on the y-axisPlace on the y-axis

Constants & ControlsConstants & Controls

ConstantConstant – – the factors that are kept the factors that are kept the same in an experiment to make the same in an experiment to make sure the experiment is valid and sure the experiment is valid and controlled (stays the same)controlled (stays the same)

ControlControl – – the measurements that the measurements that are recorded as a basis forare recorded as a basis for comparing the results (what’s comparing the results (what’s “normal”).“normal”).

Example:Example:

You are doing an experiment to see if eating ice You are doing an experiment to see if eating ice cream in the morning will help you run a cream in the morning will help you run a mile any faster.mile any faster.

The first morning you eat half a tub of The first morning you eat half a tub of Ben &Jerry’s before you start running. Ben &Jerry’s before you start running.

The second morning you eat an entire tub The second morning you eat an entire tub before you begin (watch out for cramps!)before you begin (watch out for cramps!)

What would be the independent variable & What would be the independent variable & dependent variable?dependent variable?

What would remain constant and what would What would remain constant and what would be the control?be the control?

Answer:Answer:

Independent variable (Independent variable (II decide it changes) decide it changes)

= How much ice cream.= How much ice cream.

Dependent variable (Dependent variable (DData, what’s measured)ata, what’s measured)

= Running time for a mile= Running time for a mile

Constant (Stays the same)Constant (Stays the same)

= distance, type of ice cream, = distance, type of ice cream, time of day, same person, same shoes, time of day, same person, same shoes,

ice cream vs. other sweets, same amount ice cream vs. other sweets, same amount of sleep, etc. of sleep, etc.

Control (What is “normal”) Control (What is “normal”)

= usual running time for a mile = usual running time for a mile without any ice cream at all. without any ice cream at all.

Bar GraphsBar Graphs

Good for comparing data Good for comparing data Specific #’s of specific thingsSpecific #’s of specific things

0

10

20

30

40

50

60

70

80

90

1st Qtr 2nd Qtr 3rd Qtr 4th Qtr

Circle Graphs (Pie Charts)Circle Graphs (Pie Charts)

Shows how parts relate to the whole.Shows how parts relate to the whole.

Often used for percentages. Often used for percentages.

(The whole pie = 100 %)(The whole pie = 100 %)

Line GraphsLine Graphs

Used to demonstrate continuous Used to demonstrate continuous changechange

The slope of a linear graph The slope of a linear graph

(a straight line) is constant (y=(a straight line) is constant (y=kkx)x)

In a In a direct relationshipdirect relationship, , when one variable when one variable increases, the other increases, the other also increases.also increases.

This graph also shows a This graph also shows a linear relationshiplinear relationship (it (it is a straight line)is a straight line)

In an In an inverse relationshipinverse relationship, , when one variable when one variable increases, the other increases, the other decreases.decreases.

Draw This REALLY BIG in your spiral / binder