Scientists use experiments to test a hypothesis hypothesis or answer a question question

ObservationsObservations:• Description of objects, eventsevents• May include data from all five

senses (touch/texture, smell, taste, sight, sound)

• Could be drawings, diagrams, written words

• Do not include opinionsopinions.

ObservationsObservations:• QuaLitative: description written in

words (Letters)– five senses (touch/texture, smell, taste,

sight, sound)

• QuaNtitative: description using Numbers– Measurements using measuring tools or

counting

InferencesInferences• Drawing conclusionsconclusions based on

observations• Often provide a reasonreason for the

event/object being observed.

There are two groups in a controlled experiment:

Control GroupControl Group: the set-up within the experiment that is left alone or “natural.” Measurements of the dependent variable are still taken and used to compare to the experimental group.

There are two groups in a controlled experiment:

Experimental GroupExperimental Group:: the set-up within the experiment where the researcher looks at the affect of the independent variable on the dependent variable.

The independent variable will be some factor that is present in the experimental group but not in the control group.

Example Experiment: Ketchup

Research question: is the thickness of ketchup affected by refrigeration?

• Control group: unrefrigerated ketchup

• Experimental group: ketchup at different temperatures

• Variables are factors in an experiment that are measured or controlled.

• Independent (manipulated) Independent (manipulated) variablevariable: : •factors or categories in an experiment that are tested tested by the scientistby the scientist.

**Simple experiments have only ONEONE independent variable.

Dependent (responding) Dependent (responding) variable:variable:

..the factor that you are measuring as a result of measuring as a result of the ind. variable the ind. variable .

Controlled variables Controlled variables (constants): (constants):

factors in an experiment that are kept the same for every kept the same for every groupgroup.

Example Experiment: Ketchup

Research question: is the thickness of ketchup affected by refrigeration?

• Independent variable (can be controlled by experimenter): temperatures (30° F, 60° F, and 72° F) at which ketchup is stored.

• Dependent variable (measurement taken under each experimental condition): time it takes a ketchup to drip off a spoon

• Constants (kept same for both control and experimental group): ketchup brand, amount on spoon, type of spoon, testing location, thermometer for recording temps, whether ketchup bottle gets shaken before time is measured, time stored in each temperature before being tested, etc.

Parts of an Experiment

RESEARCH QUESTION/PROBLEM

What question is being answered, problem solved, or hypothesis tested?

For example, “Is the thickness of ketchup affected by refrigeration?”

HypothesisHypothesis• An “if…then…because” statement

describing your expected results.• Always support your idea with a reason!• State it like this:

– If = your independent variable– Then = your dependent variable– Because = a scientific reason

• Always use positive language: this will (not might) occur

Parts of an Experiment

Example Experiment: Ketchup

Research question: is the thickness of ketchup affected by refrigeration?

• Hypothesis: If ketchup is stored at a colder temperature, then it will take more time to drip off a spoon because the cold temp. allows the ketchup to congeal which makes it thicker.

• Remember each variable:– Independent: storage temp.– Dependent: amount of time to drip off spoon

Procedure:Includes two things: 1. Items used during the experiment

(materials).2. Step by step directions that any other

person would be able to follow.

What materials would you need for your experiment? Write it down…

Parts of an Experiment

ProcedureProcedure:

Steps followed during experiment.– Write in a numbered list– Should be detailed enough that anyone can follow

exactly what you did.– Include the number of times you are going to do

the experiment (trials)? • The number of trials depends on the experiment, but it

should be enough to generate accurate averages. At least three trials minimum.

Parts of an Experiment

Write it down…

Example Experiment: KetchupResearch question: is the thickness of ketchup affected by refrigeration?

Materials:•Heinz Ketchup 3 20 oz. plastic bottles•Measuring spoon: 1Tbls•Thermometer (°F)•Refrigerator w/freezer•Stopwatch•Bowl

Procedure:1.Record temperatures of freezer, refrigerator and countertop in °F.2.Place one bottle of ketchup in each location.3.Allow bottles to sit for 30 minutes undisturbed.4.Take bottle out of freezer.5.Shake bottle for 10 seconds before testing.6.Open bottle and squirt 1 tablespoon of ketchup into the measuring spoon making sure ketchup is level with top of spoon.7.Replace bottle in storage area while running each trial.8.Hold spoon vertically with ketchup at bottom end over a bowl and start stopwatch.9.When the first drip of ketchup hits the bowl, stop stopwatch and record time.10.Clean and dry measuring spoon and repeat 3 more times.11.Repeat procedure for ketchup stored in refrigerator and on countertop.

Observations/Data:Observations/Data:

All the measurements gathered while performing the experiment.

Always record in a pre-made data table.

Now, do the experiment! Record your data in the table.

Parts of an Experiment

Example Experiment: KetchupResearch question: is the thickness of ketchup affected by refrigeration?

Temp (°F) Time (s)Trial 1

Time (s)Trial 2

Time (s)Trial 3

Average time (s)

Freezer

Fridge

Counter

Results/Conclusions:Results/Conclusions:Graph your data.Write an analysis of your data to determine

the final outcome of the experiment. Include the following:

• What do you NOW believe as a result of the experiment or observations?

• Restate your hypothesis (or at least relate your findings to it).

• Support your claim with at least 2 pieces of data, including averages.

• Use good explanatory language.

Parts of an Experiment

Example Experiment: KetchupResearch question: is the thickness of ketchup affected by refrigeration?

Share your results:Share your results:

Publish your findings so that others may benefit from your work.

Parts of an Experiment