a variable causing consistent shift of the mean in one direction e.g. retrospective recall of diet omits snacks
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what is random error
fluctuation of scores due to chance e.g. innaccurate description of food eaten
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what methods are used to assess error
pearson correlation (1= no error, 0.7 is the acceptable value) and the bland-altman plot
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bland-altman plot: what are the 3 points of visual assessment
systematic error (mean's closeness to the 0-line), random error (do points deviate greatly from the mean line) and nature of error (points consistent left-right e.g. funnelling)
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why is error important (2 reasons)
to determine the agreement between measurement methods and we want primary variance to outweigh systematic/error variance
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