2 Errors, Random Errors and Statistical Data in Chemical Analyses Part 1 [Sir Jameson PPT]

Question 1

One type called ________ (or indeterminate) error, causes data to be scattered more or less symmetrically around a mean value.

Answer 1

Random

Question 2

A second type of error, called ____ (or determined) error, causes the mean of set of data to differ from the accepted value.

Answer 2

Systematic

Question 3

Error that affect the precision of measurement

Answer 3

Random Error

(Indeterminate)

Question 4

Errors affects the accuracy of results

Answer 4

Systematic Error
(Determinate)

Question 5

A third type of error is _____ error.

Answer 5

Gross Error

Question 6

They usually occur only occasionally, are often large, and may cause a result to be either high or low.

Answer 6

Gross Error

Question 7

Gross Error lead to __________, results that appear to differ markedly from all other data in a set of replicate measurements.

Answer 7

Outliers

Question 8

Various ____ tests can be done to determine if a data point is an outlier.

Answer 8

Statistical

Question 9

Systematic Error have a ______, an assignable cause, and are of about of the same magnitude for replicate measurements made in the same way.

Answer 9

Definite Value

Question 10

Systematic Errors lead to __ in measurement technique. Note that _______ affects all the data in a set in approximately the same way that it bears a sign.

Answer 10

Bias

Question 11

Three types of Systematic Error

Answer 11

Instrument
Method
Personal

Question 12

Caused by imperfections in measuring devices and instabilities in their components.

Answer 12

Instrument Errors

Question 13

Arised from non-ideal chemical or physical behavior of analytical systems.

Answer 13

Method Error

Question 14

Result from the carelessness, inattention, or personal limitations of the experimenter.

Answer 14

Personal Errors

Question 15

Instrument Errors

All _______________ are sources of systematic errors.

Answer 15

Measuring Devices

Question 16

Instrument Errors

______,________ and ___________ may hold or deliver volumes slightly different from those indicated by their graduations.

Answer 16

Pipets
Burets
Volumetric Flasks

Question 17

It eliminates most systematic errors of this type.

Answer 17

Calibration

Question 18

Electronic instruments are subjects to instrumental systematic errors.

Answer 18

Instrumental Errors

Question 19

• Those uncertainties have many sources.
• Error are detectable and correctable

Answer 19

Instrument Errors

Question 20

Errors emerge as the voltage of a battery-operated power supply decreased with use.

Answer 20

Instrumental Errors

Question 21

The nonideal chemical or physical behavior of the reagents and reactions upon which an analysis based often introduce systematic method errors.

Answer 21

Method Errors

Question 22

Errors such sources of nonideality include ____ and ___________ of reactions, the instability of species, non-specificity of most reagents, and possible interference.

Answer 22

Method Errors
Slowness
incompleteness

Question 23

Method Errors

Errors inherent in a method are often difficult to detect and are thus the _________ of the three types of systematic error.

Answer 23

Most serious

Question 24

Measurements requiring personal judgments

Answer 24

Personal Errors

Question 25

Judgments of this type are often subject to systematic, unidirectional errors.

Answer 25

Personal Errors

Question 26

- An analyst who is insensitive to color changes tends to use excess reagent in a volumetric analysis. – Physical disabilities are often sources of personal determinate errors.

Answer 26

Personal Errors

Question 27

A universal source of personal error is **prejudice or bias.**

Answer 27

Personal Errors

Question 28

is another source of personal error that varies considerably from person to person.

Answer 28

Number bias

Question 29

The most common number bias encountered in estimating the position of a needle on a scale involves a preference for the digits __ and ___. Also _____is a prejudice favoring small digits over large and even numbers over odd.

Answer 29

0 5 prevalent

Question 30

amplifies personal errors in a volumetric analysis.

Answer 30

Color blindness

Question 31

Systematic errors may be either ____ or _______.

Answer 31

constant or proportional

Question 32

The magnitude of a ________ does not depend on the size of the quantity measured.

Answer 32

constant error

Question 33

______________ increase or decrease in proportion to the size of the sample taken for analysis.

Answer 33

Proportional errors

Question 34

are usually corrected by **periodic calibration of equipment.** The response of most instruments changes with time.

Answer 34

Systematic instrument errors

Question 35

Most personal errors can be minimized by _____________ and ______________

Answer 35

care and self-discipline

Question 36

Systematic instrument errors are usually corrected by ____________________ The response of most instruments changes with time.

Answer 36

periodic calibration of equipment.

Question 37

is the best way to estimate the bias of an analytical method.

Answer 37

standard reference materials, **SRMs**

Question 38

it contain one or more analytes at well-known or certified concentration levels.

Answer 38

standard reference materials, **SRMs**

Question 39

It can sometimes be prepared by synthesis.

Answer 39

standard reference materials, **SRMs**

Question 40

it can be purchased from a number of governmental and industrial sources.

Answer 40

standard reference materials, SRMs

Question 41

Detecting Systematic Method Errors

Answer 41

1. Analyzing Standard Samples 2. Using an Independent Analytical Method 3. Performing Blank Determinations 4. Varying the Sample Size

Question 42

The concentration of one or more of the components in these materials has been determined in one of three ways: (Familiarized)

Answer 42

1) by analysis with a previously validated reference method; 2) by analysis by two or more independent, reliable measurement methods; or 3) by analysis by a network of cooperating laboratories that are technically competent and thoroughly knowledgeable with the material being tested.

Question 43

Using an Independent Analytical Method – If standard samples are not available, a ____________ and ____________ can be used in parallel with the method being evaluated.

Answer 43

second independent reliable analytical method

Question 44

____________ are useful for detecting certain types of constant errors.

Answer 44

Blank determinations

Question 45

In a blank determination, or ______, all steps of the analysis are performed in the absence of a sample.

Answer 45

blank

Question 46

__________ reveal errors and correct data

Answer 46

Blank determinations

Question 47

Constant errors can often be detected by varying the sample size

Answer 47

Varying the Sample Size

Question 48

The Nature of Random Errors All measurements contain __________

Answer 48

random errors.

Question 49

a bell-shaped curve Such a plot is called a ____________ or a normal error curve.

Answer 49

Gaussian curve