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    Hey, I'm doing unit 1 cells, exchange and transport and I've noticed that they often ask about reliability, validity and accuracy of experiments they've described. In GCSE I used the mnemonic ACAR (anomalies, concordance, average, repeat) for reliability and Cool People Wear Trousers (Controlling variables, precise equipment, wide range of results, testing the right thing) for validity. Are these appropriate for AS biology because I've been confused by the mark scheme by what they want you to say. For example, you have to say you calculate a mean to ensure reliability. How do you categorise these 3 factors? I'm struggling to understand the difference between them and how to answer questions that ask about one of the factors specifically. Thanks in advance.
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    Accuracy: The accuracy of an observation, reading or measurement is the degree to which it approaches a notional ‘true’ value or outcome. For example: closeness to a line of best fit; accuracy of apparatus on percentage error.
    Precision: The ability to be exact (degree of precision).
    Reliability: The measure of confidence that can be placed in a set of observations or measurements. For example: confidence limits of statistical tests or concordance of repeats or standard deviation.
    Validity: The implication that the outcome of an activity is not being distorted by extraneous factors.

    Make of this what you will
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    I've never realised those types of questions in F211 exam
    But I would say try follow the mark scheme as much as possible, go for the mark scheme answer as OCR is very specific about what they want written.
    You don't need to learn the definitions for the OCR exam board, it's more about knowing what they are; it's often about doing something to get accurate answers
 
 
 
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