# Shared Flashcard Set

## Details

Variables
cyberphysics aid to identifying variables
21
Physics
11/04/2007

Term
 What is accuracy?
Definition
 An accurate measurement is one which is close to the true value.
Term
 What is calibration?
Definition
 This involves fixing known points and then marking a scale on a measuring instrument, between these fixed points.
Term
 What is data?
Definition
 This refers to a collection of measurements.For example: Data can be collected for the volume of a gas or the type of rubber.
Term
 What is datum?
Definition
 The singular of data.
Term
 What's a random error?
Definition
 These cause readings to be different from the true value. Random errors may be detected and compensated for by taking a large number of readings.For example: Random errors may be caused by human error, a faulty technique in taking the measurements, or by faulty equipment.
Term
 What a systematic error?
Definition
 These cause readings to be spread about some value other than the true value; in other words, all the readings are shifted one way or the other way from the true value.For example: A systematic error occurs when using a wrongly calibrated instrument.
Term
 What's a zero error?
Definition
 These are a type of systematic error. They are caused by measuring instruments that have a false zero.For example: A zero error occurs when the needle on an ammeter fails to return to zero when no current flows, or when a top-pan balance shows a reading when there is nothing placed on the pan.
Term
 What's evidence?
Definition
 This comprises data which have been subjected to some form of validation. It is possible to give a measure of importance to data which has been validated when coming to an overall judgement.
Term
 What's a fair test?
Definition
 A fair test is one in which only the independent variable has been allowed to affect the dependent variable.Care has to be taken to keep all but the independent and dependent variables constant.For example: A fair test can usually be achieved by keeping all other variables constant.
Term
 What's precision?
Definition
 The precision of a measurement is determined by the limits of the scale on the instrument being used. Precision is related to the smallest scale division on the measuring instrument that you are using. It may be the case that a set of precise measurements has very little spread about the mean value.For example: using a ruler with a millimetre scale on it to measure the thickness of a book will give greater precision than using a ruler that is only marked in centimetres.
Term
 What's reliability?
Definition
 The results of an investigation may be considered reliable if the results can be repeated. If someone else can carry out your investigation and get the same results, then your results are more likely to be reliable. One way of checking reliability is to compare your results with those of others and/or quoted values. The reliability of data can be improved by carrying out repeat measurements and calculating a mean.If the spread of results about that mean is large then the presicion is poor.
Term
 What's a true value?
Definition
 This is the accurate value which would be found if the quantity could be measured without any errors at all.
Term
 What's validility?
Definition
 Data is only valid for use in coming to a conclusion if the measurements taken are affected by a single independent variable only. Data is not valid if, for example, a fair test is not carried out or there is observer bias.For example: In an investigation to find the effect on the rate of a reaction when the concentration of the acid is changed, it is important that concentration is the only independent variable. If, during the investigation, the temperature also increased as you increased the concentration, this would also have an effect on your results and the data would no longer be valid
Term
 What is a catergoric variable?
Definition
 A categoric variable has values which are described by labels. When you present the result of an investigation like this, you should not plot the results on a line graph; you must use a bar chart or pie chart.For example: If you investigate the effect of acid on different metals, eg copper, zinc and iron, the type of metal you are using is a categoric variable.
Term
 What is a continuous variable?
Definition
 A continuous variable is one which can have any numerical value. When you present the result of an investigation like this you should use a line graph.For example: If you investigate the effect on the resistance of changing the length of a wire, the length of a wire you are using is a continuous variable since it could have any length you choose.
Term
 What is a control variable?
Definition
 A control variable is one which may, in addition to the independent variable, affect the outcome of the investigation. This means that you should keep these variables constant; otherwise it may not be a fair test. If it is impossible to keep it constant, you should at least monitor it; in this way you will be able to see if it changes and you may be able to decide whether it has affected the outcome of the experiment.
Term
 What is an independent and dependent variable?
Definition
 Often in science we are looking at 'cause and effect'. You can think of the independent variable as being the 'cause' and the dependent variable as being the 'effect'. In other words, the dependent variable is the thing that changes as a result of you changing something else.
Term
 What is a dependent variable (proper definition)?
Definition
 The dependent variable is the variable the value of which you measure for each and every change in the independent variable.You usually plot this on the Y-axis of a graph
Term
 What's an independent variable?
Definition
 The independent variable is the variable for which values are changed or selected by the investigator. In other word, this is the thing that you deliberately change to see what effect it has.You usually plot this on the X-axis of a graph
Term
 What's a discrete variable?
Definition
 You may sometimes come across this term. It is a type of categoric variable whose values are restricted to whole numbers. In other words you cannot have a 'half' of one of these. For example, the number of carbon atoms in a chain.(You can't have half an atom!)
Term
 What are ordered variables?
Definition
 You may sometimes come across this term. It is a type of categoric variable that can be ranked.For example, the size of marble chips could be described as large, medium or small.
Supporting users have an ad free experience!