1_identifying and Controlling Variables

IDENTIFYING AND CONTROLLING VARIABLES LECTURE NOTES BY MR. SYLVESTER SAIMON SIMIN MPKS

INTRODUCTION • In scientific inquiries, we investigate to find out what causes something to happen – to find the effect of one variable on another. • We investigate the effect of changing only one of the variables; we must keep the other variables constant. In this way, we can tell whether that single variable has an effect. • The idea behind identifying and controlling variables is that we must be sure that what we think caused an effect did in fact cause it. • This skill requires children to have the ability to perceive that there is more than one attribute (physical & behaviour, interactions) to given objects (concrete operational stage) Aug 26, 2009

SYLVESTER SAIMON SIMIN, JSM, MPKS

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DEFINITION • VARIABLES: – FACTORS / CONDITIONS THAT CAN CHANGE OR BE CHANGED IN AN EVENT OR SYSTEM – THINGS WITHIN AN INVESTIGATION WHICH CAN BE CHANGED OR KEPT THE SAME

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TYPES OF VARIABLES • MANIPULATED VARIABLE (INDEPENDENT VARIABLE / INPUT VARIABLES) – WHAT TO CHANGE – FACTOR OR CONDITION THAT IS INTENTIONALLY CHANGED IN AN EXPERIMENT / INVESTIGATION.

• RESPONDING VARIABLE (DEPENDENT VARIABLE / OUTCOME VARIABLE) – WHAT TO MEASURE – FACTOR OR CONDITION THAT WILL BE AFFECTED AS A RESULT OF THAT CHANGE (MV)

• CONTROLLED VARIABLE (CONSTANT VARIABLES) – WHAT TO KEEP THE SAME – FACTOR OR CONDITION THAT IS DELIBERATELY SYLVESTER SAIMON THE SIMIN, JSM,SAME) MPKS (KEPT Aug 26,NOT 2009 CHANGED 4

TYPES OF VARIABLES

MANIPULATED VARIABLE (WHAT TO CHANGE)

RESPONDING VARIABLE (WHAT TO MEASURE)

CONTROLLED VARIABLE (WHAT TO KEEP THE SAME)

FACTOR OR CONDITION THAT IS INTENTIONALLY CHANGED IN AN EXPERIMENT / INVESTIGATION TO FIND OUT WHAT EFFECT IT HAS

FACTOR OR CONDITION THAT IS AFFECTED AS A RESULT OF CHANGING THE MANIPULATED VARIABLE

FACTOR OR CONDITION THAT IS DELIBERATELY NOT CHANGED (KEPT THE SAME) TO MAKE IT A FAIR TEST

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COMPLEXITY OF VARIABLE • EACH TYPE OF VARIABLE NEEDS TO BE OBSERVED AND MEASURED. • THE DEGREE OF COMPLEXITY OF THOSE MEASUREMENTS WILL VARY ACCORDING TO THE AGE AND EXPERIENCE OF STUDENTS AND DEMANDS OF THE INVESTIGATION. • 4 CLASSES OF COMPLEXITY OF VARIABLES: – CATEGORIC : DESCRIPTIVE EG. COLOUR – DISCRETE : MEASURED IN WHOLE NUMBERS EG. NUMBER OF LEGS OF INSECTS – CONTINUOUS : MEASURED IN RANGE OF NUMBERS INCLUDING FRACTIONS/DECIMALS EG. TEMPERATURE – DERIVED : CALCULATED FROM MEASUREMENTS OF OTHER VARIABLES EG. SPEED

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COMPLEXITY OF VARIABLES

CATEGORIC VARIABLE • SIMPLE DESCRIPTIVE VARIABLE – COLOUR • NO NUMERICAL VALUE • EG: HOT, WARM, COLD, TYPE OF BIRD Aug 26, 2009

DISCRETE VARIABLE • WHOLE NUMBER VALUE – 4 BOUNCES • EG: NO. OF LEGS, POPULATION, NO. OF TABLETS • DISCONTINUOUS VARIABLE

CONTINUOUS VARIABLE • NUMERICAL VALUE ANYWHERE ALONG A CONTINUUM OF NUMBERS INC. DECIMALS • EG: TEMPERATURE, VOLUME, MASS, TIME


DERIVED VARIABLE •CALCULATED FROM OTHER VARIABLES WHICH MUST FIRST BE MEASURED •POTENTIAL ENERGY = MASS X HEIGHT X g •EG: VELOCITY, ACCELERATION, DENSITY

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KEY VARIABLES INVESTIGATION

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MANIPULATED

RESPONDING

CONTROLLED

COLOUR OF BALLS (CATEGORIC)

HEIGHT OF BOUNCE (CONTINUOUS)

• • • •

HEIGHT OF DROP SIZE OF BALL SURFACE BOUNCED ON TYPE OF BALL

COLOUR OF BALLS (CATEGORIC)

NUMBER OF TIMES IT BOUNCES AFTER A DROP (DISCRETE)

• • • •

HEIGHT OF DROP SIZE OF BALL SURFACE BOUNCED ON TYPE OF BALL

HEIGHT FROM WHICH THE BALL IS DROPPED (CONTINUOUS)

HEIGHT OF THE FIRST BOUNCE (CONTINUOUS)

• • • •

COLOUR OF BALL SIZE OF BALL SURFACE BOUNCED ON TYPE OF BALL

HEIGHT OF THE DROP INCORPORATED INTO mxgxh CALCULATION (CONTINUOUS / DERIVED)

HEIGHT OF THE FIRST BOUNCE (CONTINUOUS)

• • • •

COLOUR OF BALL SIZE OF BALL SURFACE BOUNCED ON TYPE OF BALL


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SUGGESTED APPROPRIATENESS OF VARIABLES LEVEL (YEAR/FORM)

MANIPULATED VARIABLE

RESPONDING VARIABLE

PRE-SC Y1 Y2 Y3 Y4 Y5 Y6 F1 F2 F3 F4 F5

NOT REQUIRED

NOT REQUIRED

1 1 1 CONTINUOUS 2 OR MORE VARIABLES

1 1 1 CONTINUOUS

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1, PROBABLY CONTINUOUS OR DERIVED

INCREASING COMPLEXITY

1, PROBABLY CONTINUOUS OR DERIVED


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IDENTIFYING VARIABLES: WHAT ARE THE VARIABLES IN THESE STATEMENTS?

“The time it takes to run a kilometer depend on the amount of exercise a person get” Time to run a kilometer VARIABLE : _______________________ amount of exercise VARIABLE : _______________________ NOTE: It would not be correct to name just time or exercise. We must include how each variable will be measured or described.

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“The higher the temperature of water, the faster an egg will cook” Temperature of water VARIABLE : _______________________ time needed for an egg to cook VARIABLE : _______________________

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“An investigation was done to see if keeping the light on for different amount of time each day affected the number of eggs chickens laid” Hours (or amount) of light VARIABLE : _______________________ number of eggs VARIABLE : _______________________ NOTE: Just light and eggs however, would be incorrect descriptions of the variables. IT MUST BE

MEASURABLE. Aug 26, 2009


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CLASSIFYING VARIABLES : MV, RV, CV “The amount of pollution produced by cars was measured for cars using gasoline containing different amount of lead” MANIPULATED VARIABLE : amount of lead in gasoline _______________________ RESPONDING VARIABLE : amount of pollution _______________________

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CLASSIFYING VARIABLES : MV, RV, CV “more bushels of potatoes will produced if the soil is fertilized more” MANIPULATED VARIABLE : amount of fertilizer _______________________ RESPONDING VARIABLE : number of bushels of potatoes _______________________

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CLASSIFYING VARIABLES : MV, RV, CV “Five groups of rats are fed identical diets except for the amount of Vitamin A that they receive. Each group gets a different amount. After three weeks on the diet, the rats are weighed to see if the amount of vitamin A received has affected their weight.” MANIPULATED VARIABLE : Amount of Vitamin A _______________________ RESPONDING VARIABLE : Weight of rats _______________________ NOTE: Weight of rats may not be affected if Vitamin A is not essential but the weight of rats is still the RV. Aug 26, 2009


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CLASSIFYING VARIABLES : MV, RV, CV “A student wanted to test how the mass of a paper airplane affected the distance it would fly. Paper clips were added before each test flight. As each paper clip was added, the plane was tested to determine how far it would fly” MANIPULATED VARIABLE : Number of paper clip added _______________________ RESPONDING VARIABLE : Distance flown _______________________ CONTROLLED VARIABLES : The same plane was used for each trial _______________________ Aug 26, 2009


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THANK YOU FOR YOUR ATTENTION AND COOPERATION

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1_identifying and Controlling Variables

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