Chapter 3.3 Types of Error

Question 1

Experimental Error

Answer 1

difference between the true value and the measured value of a quantity
Classified as Systematic, random, or blunder

Question 2

Systematic error

Answer 2

also called determinate error
arises from a flaw in equipment or design of the experiment
it is consistent and can be detected and corrected

Question 3

Ways to detect systematic error

Answer 3

1. Analyze known sample
2. use an alternate method to measure the same quantity
3. Participate in a round-robin with other labs
4. analyze a blank sample containing no analyte

Question 4

Ways to correct a systematic error

Answer 4

1. Calibrate glassware and instruments

2. Use standard addition or internal standard

Question 5

Certified reference materials

Answer 5

samples sold by national measurement institutes containing known quantities of analytes in a specified matrix to test the accuracy of analytical procedures

The US National Institute of standards and tech calls its certified material standard reference materials

Question 6

Random error

Answer 6

also called indeterminate error
arises from uncontrolled variables in the measurement
cannot be eliminated but might be reduced by better technique

Question 7

Blunders

Answer 7

also called gross errors
extreme instances of random or systematic error due to accidental but significant departures from the procedure
Unrecoverable errors due to procedural instrumental or clerical mistakes

Question 8

Precision

Answer 8

describes the reproducibility of a result

Question 9

Accuracy

Answer 9

How close the measured value is to the “true” value (known standard value)

Question 10

uncertainty

Answer 10

variability in measurements

Question 11

error

Answer 11

difference between the measured and “true” value

Question 12

Absolute uncertainty

Answer 12

expresses the margin of uncertainty associated with a measurement

Question 13

Relative uncertainty

Answer 13

compares the size of the absolute uncertainty with the size of its associated measurement

= Absolute uncert/ magnitude of measurement

Question 14

percent relative uncertainty

Answer 14

= 100 X relative uncertainty