MEASURING TECHNIQUES
Every measurement- not exact, degree of uncertainty/error
Systematic error- error occurs according to fixed rule/ pattern > constant (over-/under-) estimation (repeating doesn't reduce it), due to- apparatus or bad experimental technique (eg zero error, wrong assumption)
Can be reduced/eliminated by good exp techniques, checking apparatus (> make corrections- for zero error)
Random error- errors w/ diff magnitude and signs, vary slightly from mean (true) value, due to inability to obtain true value (due to limitations in accuracy or sensitivity of apparatus) (can be reduced by repeating)
Precision- ability to take to large sf, limit of sensitivity of apparatus
Accuracy- closeness to true value (limited by precision), depends on magnitude of quan measured & apparatus used- same instrument w/ same precision: measure diff magnitude > diff accuracy (small quan > high error > less accuracy)
Treatment of errors
A measurement: (X ± ΔX); actual (absolute) uncertainty; generally smallest graduation (ΔX)
% error: indicates suitability of instrument (check accuracy) = ΔX/X x 100
fractional error: ΔX/X
consequential uncertainties = overall uncertainties from diff measurements
addition/ subtraction: add absolute error
multiplication/ division: add % error [ΔR/R = ΔR1/R1 + ΔR2/R2]
exponents: multiply % error by exponent [R = R1n > ΔR/R = n ΔR1/R1]
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