# ISA Glossary Terms

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• ISA Glossary Terms
• Accuracy
• A result is considered "accurate" if it is close to the true value.
• Data
• Information that has been collected .
• Qualitative or quantitative.
• Errors
• Measurement Error
• The difference between a measured value and the true value.
• Anomalies
• Results which are judged not to be part of the variation caused by random uncertainty.
• Random Error
• Cause readings to be spread about the true value, due to results varying in an unpredictable way from one measurement to the next
• Effects can be reduced by making more measuremens and calculating a new mean.
• Systematic Error
• These cause readings to differ from the true value by a consistent amount each time a measurement is made.
• Source of this error could include: environment, methods of observation, or instruments used.
• Cannot be dealt with by simple repeats. If you suspect a systematic error, the experiment should be repeated using a different technique or equipment, Then compare results.
• Zero Error
• Measuring system gives a false reading when the true value of a measured quantity is zero.
• May result in systematic error.
• Eg. the needle of an ammeter failing to return to zero when no current flows.
• Calibration
• Marking a scale on a measuring instrument.
• Eg. Placing a thermometer in melting ice to see whether it reads zero.
• In order to check if it has been calibrated correctly.
• Evidence
• Data which has been shown to be valid.
• Fair Test
• Only the independent variable is allowed to change the dependent variable
• Hypothesis
• A proposal intended to explain certain facts or observations
• Interval
• Eg. A set of 11 readings equally spaced over a distance of 1 metre would give an interval of 10cms.
• Precision
• Depends on the extent  only random errors.
• It gives no indication of how close results are to the true value.
• Prediction
• Statement suggesting what will happen in the future.
• Based on observation, experience or a hypothesis.
• Range
• Maximum and minimum values of either variables.
• Important in ensuring a pattern is detected.
• Eg. "From 10cm to 50cm" or "From 50cm to 10cm"
• Repeatable
• If the original experimenter repeats the exact same investigation and obtains the same results. The measurements are repeatable.
• Reproducible
• If the investigation is repeated by another person using different equipment or techniques but obtains the same results the measurements are reproducible.
• Resolution
• This is the smallest change in the quantity (input) of a measuring instrument
• That gives a perceptible change.
• Sketch Graph
• A line graph which shows the general shape of the relationship between the variables.
• No points plotted.
• Labelled axes. May not be scaled.
• True Value
• Value that would be obtained in ideal measurement
• Uncertainty
• Interval within which the true value can be expected to lie.
• With a given level of confidence.
• Eg. Th temperature is 20degrees Celsius+2 degreees Celsius. At a level of confidence at 95%
• Validity
• Suitability of the investigative procedure to answer the question being asked.
• Eg. An investigation to find out if the rate of a reaction depended on the concentration of 1 of the reactants would not be a valid procedure if the temperature of the reactants was not controlled.
• Valid Conclusion
• A conclusion supported with valid data obtained from an appropriate experiment and based on sound reasoning.
• Variables
• Categoric Variables
• Variables that have values that have labels.
• eg. names of plants or types of material
• Continuous Variables
• Variables that can have values that can be given a magnitude either by counting or by measurement
• Control Variables
• A variable that has to be kept constant or at least monitored because it can affect the outcome.
• Dependent Variable
• The variable where the value is measured for each and every change in the independent variable.
• Independent Variable
• The variable in which values are changed or selected by the investigator.