IMPROVEYOURGRADES FORSCIENCE!What do Ineed torevise?
Know your experiment• Know the type of equipment you used andwhy you chose it .• Know the name of each piece of theequipment and what it does (measures - ifapplicable).• Know the sensitivity of the equipment –that should have been evident in the wayyou wrote results in the table.• Know why you chose the number ofreadings to take.
Terminology• Make sure you KNOW all of the scientifickey-words to describe variables etc.– Remember it is the independent variable thatyou change by a regular amount (and usually ploton the x-axis)– Remember it is the dependent variable that youmeasure as it changes in response to thechanges in the independent variable (usuallyplotted on the y-axis).– The control variables are kept constant to makethe results valid.This is very important whenanswering questions. usingcorrect terminologydefinitely will improve yourgrades
Why are control variables keptconstant?– If that variable had changed as well asthe independent variable the dependentvariable would have responded to thatchange too – making the experimentinvalid. Do not simply say – ‘to make it afair test’ if asked to explain why controlvariables are kept constant – expand onthe idea… and say it would affect thedependent variable.
• If you are asked ‘what you weretrying to find out’ or the ‘purpose ofyour investigation’…. they want toknow what you decided to investigate.• They want you to describe how youdecided on varying your independentvariable and observing the effect thishas on the dependent variable…• They want a brief description of the‘fair test’ you carried out…
Minimising errors• A good experimenter checks theequipment is reliable before beginning– she looks for ‘zero error’ oninstruments and calibration errorsand uses instruments of a suitableprecision.
Minimising errors• Zero errors can sometimes beadjusted manually – otherwise theycan be noted and deducted from allreadings. A column of actual readingsshould be recorded and then a columnof readings corrected for zero errorshould be drawn.
Minimising errors• Calibration errors are a bigger problem.• They can mean that all of the results are out by apercentage because two fixed points have notbeen fixed correctly.• You can spot drastic calibration errors bychecking meters against each other – but you don’tknow the whole batch may be wrong!• If you were doing an important research projectyou would check the meters against standardresistors etc. to see whether they were properlycalibrated.
Minimising errors• Using instruments with sensitivescales (small divisions – moresignificant figures) give results withmore precision.• This will not make your results morereliable or accurate (valid) – justmore precise.
Minimising errors• Any possible causes of errors spottedwhile carrying out the experiment(sparking, heating, fluctuations in themeters) are noted.• A repeat set of readings is taken tocheck the reliability of the first set…any that differ widely on repeatingmust be checked again.
How can you tell if yourreadings are reliable?• When repeated the results arevirtually the same – giving you anaverage that barely differs fromeither set.• When plotted a smooth curve orstraight line is obtained – no obviousanomalies – they make a pattern.
Is reliable the same asaccurate?• NO!!!• If there is a problem with theaccuracy of your measuringinstruments and/or an error in howyou are using the equipment you willget repeatable data that is wrong.
Conclusion• State the findings in terms of how theindependent variable affected the dependent one.• Refer to the graph shape to describe therelationship and make a conclusion from that.• Does it go through the origin?• Is it the same in negative bias as forward bias?• Does it indicate direct proportionality?• If you can use numbers do so!
Evaluation• Are your results valid for ALL componentsor only true for the one you did?• In order to make a more general conclusionhow many others would you have to test?• Would you expect all of the results to beidentical?• What tolerance would you allow?