NOTE SHEET 1 – NOTE SHEET 1 – Designing Controlled Designing Controlled

ExperimentsExperiments

Why?Why?

Scientists can solve problems and test Scientists can solve problems and test theories by designing and performing theories by designing and performing controlled experimentscontrolled experiments

In a controlled experiment, the scientist In a controlled experiment, the scientist chooses something to test (an chooses something to test (an independent variableindependent variable) to see if it causes ) to see if it causes a change in something else that they will a change in something else that they will measure (the measure (the dependent variabledependent variable))

The experiment is controlled because the The experiment is controlled because the scientist makes sure that all experimental scientist makes sure that all experimental variables are kept constant and only variables are kept constant and only changes the independent variable changes the independent variable

By doing this, the scientist makes sure By doing this, the scientist makes sure that the dependent variable can only that the dependent variable can only change if the independent variable causes change if the independent variable causes it to do soit to do so

Designing Controlled Designing Controlled ExperimentsExperiments

For example, a scientist could see if For example, a scientist could see if caffeine (IV)caffeine (IV) affects affects growth (DV)growth (DV) in mice in mice

A controlled experiment has 4 basic A controlled experiment has 4 basic parts:parts:1.1. THE PROBLEMTHE PROBLEM – What are you trying to – What are you trying to

find out? find out? Independent Variable (IV)Independent Variable (IV) – What is – What is

tested to see if it has an effect on tested to see if it has an effect on something elsesomething else

Dependent Variable (DV)Dependent Variable (DV) – What is – What is affected or changed because of the IV – affected or changed because of the IV – The DV in a controlled experiment is The DV in a controlled experiment is what you measure as your datawhat you measure as your data

Problem StatementProblem Statement – Question that – Question that relates the IV to the DVrelates the IV to the DV

How will the How will the IV IV affect the affect the DV DV ??

HypothesisHypothesis

A hypothesis is a prediction based on prior A hypothesis is a prediction based on prior research about what will happen during the research about what will happen during the experimentexperiment

For the problem For the problem “How will caffeine affect “How will caffeine affect growth in mice?”growth in mice?” there are a few possible there are a few possible hypotheses:hypotheses: The caffeine will have a negative effect The caffeine will have a negative effect

on the growth of the miceon the growth of the mice The caffeine will have a positive effect The caffeine will have a positive effect

on the growth of the miceon the growth of the mice The caffeine will have no effect on the The caffeine will have no effect on the

growth of the micegrowth of the mice

A controlled experiment has 4 basic A controlled experiment has 4 basic parts:parts:

2.2. THE EXPERIMENTAL DESIGNTHE EXPERIMENTAL DESIGN (or (or PROCEDUREPROCEDURE) – What are you going to do ) – What are you going to do to investigate the problem?to investigate the problem?

The procedure is the steps you are going The procedure is the steps you are going to follow to do the experimentto follow to do the experiment

A good procedure is:A good procedure is:

clearly written in numbered stepsclearly written in numbered steps as precise and exact as possible as precise and exact as possible

(include measurements, units, etc.)(include measurements, units, etc.) easily repeated by somebody elseeasily repeated by somebody else

Why does the procedure have Why does the procedure have to be as precise and exact as to be as precise and exact as

possible?possible? Consider the following cake recipe:Consider the following cake recipe: Ingredients: sugar, butter, eggs, vanilla Ingredients: sugar, butter, eggs, vanilla

extract, flour, baking powder, milkextract, flour, baking powder, milk Directions: Heat oven and grease pan. Directions: Heat oven and grease pan.

Mix sugar and butter, add eggs and stir in Mix sugar and butter, add eggs and stir in vanilla. Combine flour and baking vanilla. Combine flour and baking powder and add to sugar mixture. Add powder and add to sugar mixture. Add milk and stir. Pour batter into pan and milk and stir. Pour batter into pan and bake.bake.

What is wrong with this recipe?What is wrong with this recipe?

A Better A Better RecipeRecipe

IngredientsIngredients 1 cup white sugar1 cup white sugar ½ cup butter½ cup butter 2 eggs2 eggs 2 teaspoons vanilla 2 teaspoons vanilla

extractextract 1 ½ cups all 1 ½ cups all

purpose flourpurpose flour 1 ¾ teaspoons 1 ¾ teaspoons

baking powderbaking powder ½ cup milk½ cup milk

DirectionsDirections1.1. Preheat oven to 350 degrees Preheat oven to 350 degrees

F (175 degrees C). Grease F (175 degrees C). Grease and flour a 9x9 inch pan or and flour a 9x9 inch pan or line a muffin pan with paper line a muffin pan with paper liners. liners.

2.2. In a medium bowl, cream In a medium bowl, cream together the sugar and together the sugar and butter. Beat in the eggs, one butter. Beat in the eggs, one at a time, then stir in the at a time, then stir in the vanilla. vanilla.

3.3. Combine flour and baking Combine flour and baking powder, add to the creamed powder, add to the creamed mixture and mix well. mixture and mix well.

4.4. Finally stir in the milk until Finally stir in the milk until batter is smooth. Pour or batter is smooth. Pour or spoon batter into prepared spoon batter into prepared pan.pan.

5.5. Bake for 30 to 40 minutes in Bake for 30 to 40 minutes in the preheated oven. For the preheated oven. For cupcakes, bake 20 to 25 cupcakes, bake 20 to 25 minutes. Cake is done when minutes. Cake is done when it springs back to the touch. it springs back to the touch.

Mmmm…CakeMmmm…Cake

Experimental Design Experimental Design ContinuedContinued

ConstantConstant – Variables in the – Variables in the experiment that remain the same experiment that remain the same each trialeach trial

ControlControl – A test group without the IV – A test group without the IV used for comparison to see if the IV used for comparison to see if the IV really has any affect on the DVreally has any affect on the DV

Repeated TrialsRepeated Trials – Doing tests more – Doing tests more than once to get more accurate datathan once to get more accurate data

Does shampoo Does shampoo work?work?

If you ALWAYS wash If you ALWAYS wash your hair with your hair with shampoo, how do you shampoo, how do you know if it actually know if it actually works?works?

If you try washing your If you try washing your hair with just water, hair with just water, and it looks and feels and it looks and feels the same, does the the same, does the shampoo do anything?shampoo do anything?

Would you know this Would you know this without trying just without trying just water?water?

In this example, using In this example, using water only would be water only would be considered a control – considered a control – this way you would this way you would know if the shampoo know if the shampoo works better or worse works better or worse than nothing at allthan nothing at all

Why repeat Why repeat trials?trials?

If you flip a coin one If you flip a coin one time and get heads, is time and get heads, is this a correct this a correct conclusion: conclusion:

Every time you flip a Every time you flip a coin, you get headscoin, you get heads

If you flip the coin a few If you flip the coin a few more times, eventually more times, eventually you will get a tailsyou will get a tails

If you get a result once, If you get a result once, it is meaningless, but if it is meaningless, but if the experiment is the experiment is repeated and the repeated and the results are always the results are always the same, then that result same, then that result is reliableis reliable

A controlled experiment has 4 basic A controlled experiment has 4 basic parts:parts:3.3. THE DATATHE DATA – A measure of the IV’s effect – A measure of the IV’s effect

on the DVon the DV Data is collected and presented in a Data is collected and presented in a Data Data

TableTable AND a AND a GraphGraph

Data Table and GraphData Table and Graph

In a data table, the IV goes in the left In a data table, the IV goes in the left column and the DV goes in the right column and the DV goes in the right columncolumn

In a graph, the IV is on the X-axis In a graph, the IV is on the X-axis (bottom) and the DV is on the Y-axis (bottom) and the DV is on the Y-axis (left side)(left side)

A controlled experiment has 4 basic A controlled experiment has 4 basic parts:parts:

4.4. THE CONCLUSIONTHE CONCLUSION – An answer to – An answer to the problemthe problem

A conclusion uses data to answer the A conclusion uses data to answer the question asked by the problem question asked by the problem statement and discusses the statement and discusses the experiment’s experiment’s validityvalidity

A good conclusion is always A good conclusion is always supported by data from the graph supported by data from the graph and data tableand data table

Why do I need to back up the Why do I need to back up the conclusion with data?conclusion with data?

Consider the Consider the following following statement by itself:statement by itself:

Michael Jordan is Michael Jordan is the greatest the greatest basketball player in basketball player in the history of the the history of the NBANBA

The Same The Same Statement Statement With DataWith Data

Michael Jordan is the Michael Jordan is the greatest basketball player greatest basketball player in the history of the NBAin the history of the NBA

NBA 50th Anniversary All-NBA 50th Anniversary All-Time Team (1996) Time Team (1996)

Member of six NBA Member of six NBA championship teams championship teams (1991-93, 1996-98)(1991-93, 1996-98)

Five-time NBA Most Five-time NBA Most Valuable Player (1988, Valuable Player (1988, 1991-92, 1996, 1998)1991-92, 1996, 1998)

Six-time NBA Finals Most Six-time NBA Finals Most Valuable Player (1991-93, Valuable Player (1991-93, 1996-98)1996-98)

Ten-time All-NBA First Ten-time All-NBA First Team (1987-93, 1996-98) Team (1987-93, 1996-98)

All-NBA Second team All-NBA Second team (1985)(1985)

Michael Jordan Michael Jordan is the is the

greatest…greatest… Nine-time NBA All-Nine-time NBA All-

Defensive First Team Defensive First Team (1987-93, 1996-98)(1987-93, 1996-98)

NBA Defensive Player NBA Defensive Player of the Year (1988)of the Year (1988)

NBA Rookie of the NBA Rookie of the Year (1985) Year (1985)

NBA All-Rookie Team NBA All-Rookie Team (1985)(1985)

Two-time IBM Award Two-time IBM Award winner, for all-around winner, for all-around contribution to team's contribution to team's success (1985, 1989)success (1985, 1989)

Three-time NBA All-Three-time NBA All-Star Game MVP Star Game MVP (1988, 1996, 1998)(1988, 1996, 1998)

Participated in 11 NBA Participated in 11 NBA All-Star Games (1985, All-Star Games (1985, 1987-1993, 1996-98), 1987-1993, 1996-98), starting 10 times, and starting 10 times, and missed another due missed another due to injuryto injury

Holds the NBA All-Star Holds the NBA All-Star Game career record Game career record for highest scoring for highest scoring average (21.3 ppg)average (21.3 ppg)

Recorded only triple-Recorded only triple-double in All-Star double in All-Star Game history, with 14 Game history, with 14 points, 11 rebounds points, 11 rebounds and 11 assists, in the and 11 assists, in the 1997 NBA All-Star 1997 NBA All-Star Game in ClevelandGame in Cleveland

Michael Jordan Michael Jordan is the is the

greatest…greatest… Won the Nestle Crunch Won the Nestle Crunch Slam Dunk in 1987 and Slam Dunk in 1987 and 1988, also participating in 1988, also participating in 19851985

Passed Kareem Abdul-Passed Kareem Abdul-Jabbar to become the Jabbar to become the NBA's all-time leading NBA's all-time leading playoff scorer (5,762 playoff scorer (5,762 points) during the 1998 points) during the 1998 Eastern Conference FinalsEastern Conference Finals

Passed Dennis Johnson Passed Dennis Johnson into fourth place on the into fourth place on the NBA's all-time playoff NBA's all-time playoff assists list (1,006), in an assists list (1,006), in an 88-83 victory over the 88-83 victory over the Indiana Pacers in Game 7 Indiana Pacers in Game 7 of the Eastern Conference of the Eastern Conference Finals in 1997-98Finals in 1997-98

Scored his 29,000th Scored his 29,000th career point, posting career point, posting a game-high 41 a game-high 41 points, 6 rebounds points, 6 rebounds and 4 assists, in a and 4 assists, in a 107-93 win over the 107-93 win over the Minnesota Minnesota Timberwolves on 4/3Timberwolves on 4/3

Broke Kareem Abdul-Broke Kareem Abdul-Jabbar's NBA record Jabbar's NBA record by scoring in double-by scoring in double-digits for the 788th digits for the 788th consecutive game, consecutive game, scoring a game-high scoring a game-high 33 points, against the 33 points, against the Minnesota Minnesota Timberwolves on Timberwolves on 12/30/9712/30/97

Scored a career-high Scored a career-high 69 points in a 117-69 points in a 117-113 overtime win at 113 overtime win at Cleveland on 3/28/90Cleveland on 3/28/90

The Conclusion Continued - The Conclusion Continued - ValidityValidity

ValidityValidity – How reliable are the – How reliable are the results of an experiment?results of an experiment?

Results are more reliable, or valid, Results are more reliable, or valid, when:when: the experiment is repeated more than the experiment is repeated more than

once (repeated trials)once (repeated trials) The experiment is carefully designed The experiment is carefully designed

and performed and performed The experiment keeps all variables The experiment keeps all variables

constant (except for the IV)constant (except for the IV)

The results of an experiment The results of an experiment are not valid if…are not valid if… All the variables in the experiment are All the variables in the experiment are

not carefully controllednot carefully controlled The procedure does not include The procedure does not include

measurementsmeasurements The experiment is done only one timeThe experiment is done only one time If mistakes are made during the If mistakes are made during the

experiment that might affect the resultsexperiment that might affect the results

Experimental ScenarioExperimental Scenario A science teacher heard a rumor that A science teacher heard a rumor that

students listening to classical music students listening to classical music perform better on tests. He decides to perform better on tests. He decides to test this theory when he gives his next test this theory when he gives his next test to his class, which contains 20 test to his class, which contains 20 students. Design a controlled experiment students. Design a controlled experiment to test this theory. to test this theory.

DirectionsDirections First, state the problem and First, state the problem and identify the variables. Second, write a identify the variables. Second, write a numbered procedure that shows how the numbered procedure that shows how the experiment will be performed.experiment will be performed.

Experimental ScenarioExperimental Scenario

Problem StatementProblem Statement How will How will listening to classical musiclistening to classical music

affect the affect the student’s performance on student’s performance on teststests??

IV is listening to classical musicIV is listening to classical music DV is student’s performance on testsDV is student’s performance on tests