Ch 6 Random Errors in Chemical Analysis

Question 1

A bell-shaped curved

Answer 1

Gaussian curve

Question 2

The difference between the highest and lowest result

Answer 2

Spread

Question 3

What are the 4 sources of random uncertainties in the calibration of pipet

Answer 3

1. Visual judgements
2. Variation in the drainage time and angle of the pipet
3. temperature fluctuations
4. vibrations and drafts

Question 4

Is the collection of all measurements of interest to the experimenter

Answer 4

Population

Question 5

A subset of measurement selected from the population

Answer 5

sample

Question 6

Refers to the quantities such as m and o that define a population or distribution

Answer 6

Parameter

Question 7

The arithmetic average of a limited sample drawn from a population of data

Answer 7

Sample mean

Question 8

The true value for the measured quantity

Answer 8

Population mean

Question 9

A measure of the precision of the population

Answer 9

Population standard deviation

Question 10

Formula for population standard deviation

Answer 10

o =

Question 11

Represents the
deviation of a result from the
population mean relative to
the standard deviation.

Answer 11

Quantity z

Question 12

The square of the
standard deviation

Answer 12

Variance

Question 13

A normal error curve has several general properties:

Answer 13

(a) The mean occurs at the
central point of maximum frequency,
(b) there is a symmetrical distribution of positive
and negative deviations about the maximum, and
(c) there is an exponential
decrease in frequency as the magnitude of the deviations increases.

Question 14

Formula for sample standard deviation

Answer 14

s =

Question 15

The N-1

Answer 15

The number of degrees of freedom

Question 16

is the standard deviation of a
set of data divided by the square
root of the number of data points
in the set.

Answer 16

Standard error of the mean

Question 17

Formula of Standard error of the mean

Answer 17

sm = s/ square root of N

Question 18

If we have several subsets of data, a better estimate of the population standard
deviation can be obtained by ______ the data instead of using only
one data set.

Answer 18

Pooling/ std pool

Question 19

Equation of SD pool?

Answer 19

S pooled =

Question 20

is an estimate of the population variance s2

Answer 20

sample variance

Question 21

is
a curve that shows the symmetrical distribution
of data around the mean of
an infinite set of data

Answer 21

A Gaussian, or normal error curve

Question 22

is the percent relative standard deviation.

Answer 22

coefficient of variation, CV,

Question 23

recommends that the symbol
sr be used for relative sample
standard deviation and o’r for
relative population standard
deviation.

Answer 23

International Union of
Pure and Applied Chemistry, IUPAC

Question 24

is another term that is sometimes used to describe the precision
of a set of replicate results. It is the difference between the largest value in the set and
the smallest.

Answer 24

Spread or range

Question 26

For a sum or a difference, the standard deviation of the answer is the square root of the sum of the squares of the standard deviations of the numbers used in the calculation

Answer 26

True

Question 27

If we have several subsets of data, a better estimate of the population standard deviation can be obtained by ______ the data instead of using only one data set. Again

Answer 27

Pooling/ SD pooled

Question 28

Formula for S pooled

Answer 28

==

Question 29

is equal to the square of the standard deviation.

Answer 29

Variance

Question 30

is an estimate of the population variance s2

Answer 30

Sample variance

Question 31

is the percent relative standard deviation.

Answer 31

coefficient of variation, CV,

Question 32

Can be obtain by dividing the standard deviation by the mean value of the data set.

Answer 32

RSD

Question 33

is another term that is sometimes used to describe the precision of a set of replicate results. It is the difference between the largest value in the set and the smallest.

Answer 33

Spread or range

Question 34

For multiplication or division, the relative standard deviation of the answer is the square root of the sum of the squares of the relative standard deviations of the numbers that are multiplied or divided.

Answer 34

True

Question 35

A much less satisfactory but more common indicator of the quality of data

Answer 35

Significant figure convention

Question 36

The __________ in a number are all of the certain digits plus the first uncertain digit.

Answer 36

Significant figure

Question 37

Rules for determining the number of significant figures:

Answer 37

1. Disregard all initial zeros. 2. Disregard all final zeros unless they follow a decimal point. 3. All remaining digits including zeros between nonzero digits are significant.

Question 38

It is especially important to postpone rounding until the calculation is completed.

Answer 38

True

Question 39

What do you call that one extra digit beyond the significant digits, which should be carried through all of the computations in order to avoid a rounding error

Answer 39

Guard digit