•Experimental Design Research – Themanipulation and control of variables • You absolutely, positively have to know what the variables are! 1. What you are changing? • How you are changing it? 2. What you are measuring? • How you are measuring? 3. Repeated trials 4. Data tables
So an experimental question has to indicate the variables:1. How the independent variable will AFFECT the dependent variable2. What the EFFECT of the independent variable will be on thedependent variable
For example…•How does the temperature ofocean water affect the speed of ahurricane? Independent variable is the temperature of ocean water. Dependent variable is the speed of a hurricane.
• Descriptive Design Research - Based mainly on observations. Ex. 1. Making models 2. Dissections 3. Observing animals in the wildSpecific Example: How do the survivorsof a disaster react to the disaster?No variables; data is based onwatching and talking to survivors
•Good questions come fromcareful observations.•Questions beginning withwhat, why, how and when arevery important in focusingon an investigation.
•An observation is anyuse of the senses togather information.•Observations may bedirect or indirect.
•Direct observations are made using one of your senses such as sight or touch.•Indirect observations are made byusing an instrument such as athermometer or a microscope.
•Observations usually lead toinferences.•An inference is a logicalinterpretation based onobservations or priorknowledge (schema).
•Example of anobservation: Shadowscan change in length.•Example of an inference: Thelength of an object’s shadowdepends on how near the objectis to the light source.
•Determine if thefollowing examples areobservations orinferences.•You do not have to write these inyour notes.
I turn on a fan.The blades of the fanare turning.
•A hypothesis is a clear statement ofwhat you EXPECT the answer to yourquestion to be.•Your hypothesis will represent yourbest “educated guess” based on whatyou have observed and what youalready know (schema).•A hypothesis must be stated in an if-then format.
A hypothesis is a special kind ofprediction. o What makes it so special???• It’s a guess about the VARIABLES&their relationship, in particular,•How will the independentvariable affect the dependentvariable?
Here is an example of ahypothesis:If the researcher uses acidrain to water plants, thenthe plants’ growth will beslower.
Do NOT use personal pronouns!!Ithink that acid raincauses plants to grow more slowly.
•Hypothesis − a statement that uses a few observations − an idea based on observations without experimental evidence•Theory − uses many observations and has lots of experimental evidence − can be applied to unrelated facts and new relationships − flexible enough to be modified if new data/evidence is introduced•Law − stands the test of time, often without change − experimentally confirmed over and over − can create true predictions for different situations − has uniformity and is universal
• You test your hypothesisby doing an experiment.• Make sure you are doingan experiment and not ademonstration!
•Experiment vs. Demonstration•Though modeling avolcano’s eruptionis an interestingdemonstration, it isNOT an experiment.•Figuring out how altitudeaffects the boiling point of wateris an experiment.
A controlled experiment testsonly ONE factor.• A controlled experiment has acontrol group and one or moreexperimental group.• The control group and theexperimental groups areEXACTLY the same except forONE factor.
• The factor that differs iscalled the variable.• Because the variable is theonly factor that differs,scientists know that this factoris responsible for the results ofthe experiment.
•An independent variableis whatthe scientist changes in theexperiment.•A dependent variableis whatchanges in the experiment as aresult of what the scientist does.
•While doing the experiment, besure to write down all of theobservations that you make.•Include any type of measurementusing the metric system.•EX: time, date, height, size,amount, temperature, etc.
•Be as exact as possible intaking measurements.•Measure something morethan once and use theaverage of the results.
Test More than One Subject!• Sample size is the number ofsubjects you test.•Your sample size must be largeenough to allow you to drawaccurate conclusions from yourdata.
•Do Multiple Trials!•When doing anexperiment, perform eachtest several times.
After you havecollected your data,determine what itmeans.
Tables and graphs are often usefulin helping to organize the data.Distance Rolled for a Metal Sphere
All graphs should include:•Title•Label the axis•Include a key (legend)•Use distinct colors
•Every graph always needs a key so people can easily tell what each color or pattern represents.
In a line graph, place the dependent variable on the vertical axis and theindependent variable on the horizontal axis.
Temperature Variation over 4 Hours605040302010 0 1 2 3 4 Sample 1 Sample 2 Sample 3
•Showing percentages iseasy to do with a pie chart.•You can quickly see whichgroup has the biggest sliceand therefore contains themost data.
Sneezing After Exposure to10 Minutes of Bright Light People who People sneezed who 43% didnt sneeze 57%
•Based on the analysis of yourdata, you should concludewhether your results rejector support your hypothesis.•If the data does reject orsupport the hypothesis, whydo you think it does?
•REMEMBER that it is NOTimportant for the hypothesis to becorrect.•What is important is that youexplain WHY you got the results youdid.•Be sure to mention in yourconclusion what factors you believecontributed to your results.
•Briefly explain possibilities fornew experiments that wouldcontrol these factors.•Also, mention any investigativequestions that came up duringthe experiment.
•Report your results bydoing a written report.•Let others know whatyou have learned.•Once again, DO NOTuse personal pronouns!!
• Be sure to include abibliography, and no, Wikipedia isNEVER an acceptable source forany project throughout the entireyear!• Give credit to the people whohelped you in your project- yourteacher, your parents,professional scientist, or others.