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CHM020 - Analytical Methods for Biology > Chapter 10: Summary > Flashcards

Chapter 10: Summary Flashcards

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1
Q

all measurements contain __ and __

A
  • errors
  • uncertainties
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2
Q

what is always provided

A
  • estimate of quality
  • reliability of collected data
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3
Q

what is prepared to improve the reliability of results

A

two to five replicate samples

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4
Q

what is used as a measure of central value of data

A
  • mean or
  • median
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5
Q

what is measured to demonstrate reproducibility of data

A

precision

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6
Q

why is it often more difficult to determine the accuracy of results than the precision

A

because true value is seldom known

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7
Q

precise measurements are not __ all of the time

A

accurate

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8
Q

arise from experimental variables that cannot be controlled or determined

A

Random or indeterminate errors

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9
Q

Random error affect __

A

precision

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10
Q

occur when instruments or measuring devices are uncalibrated or are calibrated improperly

A

Systematic or determinate errors

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11
Q

caused by nonideal instrument behavior, by faulty calibrations, or by use under inappropriate conditions

A

instrumental errors

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12
Q

arise from nonideal chemical or physical behavior of analytical systems

A

method errors

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13
Q

result from carelessness, inattention, or personal limitations of the experimenter

A

personal errors

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14
Q

are independent of the size of the sample being analyzed

A

constant errors

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15
Q

decrease or increase in proportion to the size of the sample

A

proportional errors

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16
Q

most personal errors can be minimized by what

A
  • careful, disciplined laboratory work
  • careful choice of methods and instruments
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17
Q

what is best way to estimate the bias of an anlytical method

A

analyzing standard reference materials (SRMs)

18
Q

contains the solvent and all the reagents in an analysis

A

blank

19
Q

blank that contain added constituents to simulate the __ __

A

sample matrix

20
Q

refers to the collection of all the constituents in the sample

A

matrix

21
Q

Random, or indeterminate, errors affect measuremetn __

A

precision

22
Q

where do random errors arise from

A

experimental variables that cannot be controlled or determined

23
Q

Example of random errors

A
  1. random fluctuations in electrical noise
  2. random inconsistencies in measurement readings
  3. random changes in laboratory temperature
24
Q

systematic, or determinate, errors affect the __ of results

A

accuracy

25
Q

systematic errors often occur when?

A

instruments or measuring devices are uncalibrated or calibrated improperly

26
Q

systematic errors can be very __ and __ to detect

A
  • subtle
  • difficult
27
Q

substance being determined

A

analyte

28
Q

occur infrequently and often result from an experimental blunder such as misreading a scale or interpreting a number incorrectly

A

gross errors

29
Q

occasional result in replicate measurements that differs significantly from the other results

A

outlier

30
Q
  • measures the systematic error associated with an analysis
  • has negative sign if it causes the results to be low and positive sign otherwise
A

bias

31
Q

sign of bias if it causes results to be low

A

negative sign

32
Q

sign of bias if it causes results to be high

A

positive sign

33
Q
  • determines the relationship between a measured quantity and the analyte concentration
  • very important part of any analytical procedure
A

calibration

34
Q

Of the three types of systematic errors encountered in a chemical analysis, what is usually the most difficult to identify and correct

A

method errors

35
Q

independent of the size of the sample being analyzed

A

constant errors

36
Q

decrease or increase in proportion to the size of the sample

A

proportional errors

37
Q

Equation for Mean

A

x̄ = sum of all measurements / no. of measurements

38
Q

Equation for Absolute Error

A

E = xi - xt

39
Q

Equation for Deviation from the mean

A

di = |xi - x̄ |

40
Q

Equation for Relative Error

A

Er = (xi - xt/ xt) x 100%

CHM020 - Analytical Methods for Biology (22 decks)

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