Deck 1: Making Good Measurements

Question 1

Metrology is best described as

A) The science of making measurements
B) Characterization of scientific meters
C) The process of obtaining reliable weights
D) A process that each forensic laboratory develops for forensic chemical analysis

Answer 1

A

Question 2

Data that is fit for purpose

A) does not have to be falsifiable
B) cannot be generated for most cases so we just do the best that we can
C) is always reported in SI units
D) answers the relevant question clearly and completely
E) None of the above

Answer 2

D

Question 3

All of the following are characteristics of "good data" as defined in this course except

A) Falsifiability
B) Reasonable
C) Fit for purpose
D) Defensible
E) Reliable
F) Trick question - all apply

Answer 3

F

Question 4

The NUSAP system

A) Is used in courtrooms to vet scientific experts
B) Guarantees that data is correct
C) replaced the discredited OLDSAP system
D) provides a framework for ensuring that quantitative data is clear and complete

Question 5

A forensic toxicology report states that:
"The concentration of heroin in the blood was 0.031 ug/mL ± 0.05 ug/mL"
What element(s) of the NUSAP system are missing? Mark all that apply.

A) The number
B) The units
C) The spread
D) The assessment
E) The pedigree

Question 6

What does the "pedigree" term in the NUSAP system refer to?

A) The breed of a drug-sniffing dog
B) The system within a forensic laboratory that stands behind the data that it reports
C) The calibration certificates of analytical balances used in casework
D) The training and experience of the analyst

Question 7

The term uncertainty in forensic chemistry refers to

A) The doubt associated with a number or result
B) The spread or variation of data
C) The accuracy of a result
D) The different type of units that can be used to report a number
E) The error
F) None of the above

Question 8

When dealing with significant figures, the best practice is usually to

A) Panic, as I don't like or understand significant figures
B) Round after every step
C) Ignore it and hope it goes away
D) Round at the end of the full calculation
E) Clear the calculator after each step and re-enter to be sure it is right

Question 9

The number of significant digits in a number is defined as

A) All the digits we are certain of, plus one
B) All digits to the right of the decimal point
C) All digits to the left of the decimal point
D) All digits that are retained by a calculator or spreadsheet
E) All the digits that are retained when scientific notation is used

Question 10

Data obtained from a digital measuring device or instrument is always better than data from an analog device

Question 11

Significant figures ultimately arise from

A) Math and trigonometry
B) Rounding rules
C) Metrological conventions and standards
D) Instruments used to obtain measurements

Question 12

A result from a forensic chemistry analysis is reported as 1274. ug/L

A) There are zeros implied; the result can be read as 1274.000..
B) There are four significant digits
C) Because of how the measurement was made, the rounding procedure is not clear
D) The value was rounded from 0.5

Question 13

A drug seizure weight is reported as:
85.33 g 0.04 g
The spread (uncertainty) is reported in

A) Absolute uncertainty
B) Relative uncertainty
C) Neither
D) Both

Question 14

A seizure of heroin is analyzed to obtain the %purity of the drug. An intermediate calculation involves the weight of the sample which is recorded at 75.54 mg. The balance uncertainty is 0.31 mg.
What is the relative uncertainty of the sample weight reported to two significant digits?

A) 0.0024
B) 243.7
C) 0.4
D) 0.0041
E) None of the above

Question 15

An analytical syringe used to inject samples into a GC has an absolute uncertainty of 0.05 uL. What is the relative uncertainty of a 2.5 uL injection?

A) 25%
B) 0.05 uL
C) 50%
D) 0.50
E) None of the above

Question 16

The tolerance of a pipette used in dilutions is listed as 1.0%. If the pipette is used to deliver 15.0 mL, what is the absolute uncertainty?

A) 1.5%
B) 0.15 mL or 150 uL
C) 1.5 mL
D) 15.0 uL
E) None of the above

Question 17

An analyst prepares a diluted standard for use in a post-mortem toxicological assay. The analyst dilutes 2.0 uL of a commercial standard, 1.00 mg/mL, to 10.00 mL in a type A volumetric flask. A syringe is used to draw out and deliver the 2.0 uL. The absolute uncertainties of the equipment are:
Volumetric flask: 0.08 mL
Syringe: 0.10 uL
Commercial standard: 0.050 mg/mL
What is the final concentration of the diluted solution in ug/mL? WATCH THE UNITS and report to the correct number of significant figures

A) 20.0
B) 0.0020
C) 2.00
D) 120.0
E) 0.120
F) 1.20

Question 18

An analyst prepares a diluted standard for use in a post-mortem toxicological assay. The analyst dilutes 2.0 uL of a commercial standard, 1.00 mg/mL, to 10.00 mL in a type A volumetric flask. A syringe is used to draw out and deliver the 2.0 uL. The absolute uncertainties of the equipment are:
Volumetric flask: 0.08 mL
Syringe: 0.10 uL
Commercial standard: 0.050 mg/mL
What is the uncertainty of the diluted solution expressed in ug/mL? Report to 2 decimal places

A) 14.00
B) 0.070
C) 2.00
D) 0.14
E) 1.35
F) 13.50

Question 19

You are working as a seized drug analyst in a forensic laboratory. You receive an exhibit to analyze that consists of a large ziplock bag containing brown powder. You homogenize it, select 9 samples at random, and determine the concentration of heroin in each. You calculate a mean and standard deviation value as well. The resulting values are best considered as

A) the sample mean and sample standard deviation
B) the sample mean and the population standard deviation
C) the population mean and the sample standard deviation
D) the population mean and the population standard deviation

Question 20

Why do we use the sample standard deviation for smaller data sets, such as those with less than 20 samples?

A) It's easier to calculate for smaller data sets
B) With smaller sample sets, the standard deviation of the parent population is often overestimated
C) With smaller sample sets, the standard deviation of the parent population is often underestimated
D) Significant figures get jumbled with small data sets
E) I wish I knew. Truly I do.

Question 21

An analyst is assigned a blind quality control sample of blood containing a drug metabolite. He tests ten separate portions and obtains the following data for the concentration in ug/mL:
25.2
24.8
26.6
27.0
24.0
26.0
25.5
26.3
24.9
23.9
Calculate the mean value and report to three significant figures. Use a spreadsheet or calculator

A) 12.328
B) 23.7
C) 25.0
D) 25.4
E) 24.9

Question 22

An analyst is assigned a blind quality control sample of blood containing a drug metabolite. He tests ten separate portions and obtains the following data for the concentration in ug/mL:
25.2
24.8
26.6
27.0
24.0
26.0
25.5
26.3
24.9
23.9
Calculate the sample standard deviation and report to three significant figures. Use a spreadsheet or calculator.

A) 0.995
B) 1.06
C) 9.95
D) 1.00
E) 23.0

Question 23

An analyst is assigned a blind quality control sample of blood containing a drug metabolite. He tests ten separate portions and obtains the following data for the concentration in ug/mL:
25.2
24.8
26.6
27.0
24.0
26.0
25.5
26.3
24.9
23.9
Calculate the population standard deviation and report to three significant figures. Use a spreadsheet or calculator.

A) 1.00
B) 1.06
C) 9.95
D) 1.22
E) 0.106

Question 24

An analyst is assigned a blind quality control sample of blood containing a drug metabolite. He tests ten separate portions and obtains the following data for the concentration in ug/mL:
25.2
24.8
26.6
27.0
24.0
26.0
25.5
26.3
24.9
23.9
Calculate the %RSD using the sample standard deviation and report to two significant figures. Use a spreadsheet or calculator.

A) 3.9
B) 1.5
C) 4.2
D) 4.8

Question 25

An analyst is assigned a blind quality control sample of blood containing a drug metabolite. He tests ten separate portions and obtains the following data for the concentration in ug/mL:
25.2
24.8
26.6
27.0
24.0
26.0
25.5
26.3
24.9
23.9
The accepted true value of this sample is 24.7 ug/mL. What is the absolute error between the mean obtained by the analyst and the accepted true value? Report to two significant figures

A) -1.30
B) 0.72
C) 0.93
D) -0.99
E) 1.01
F) -0.77

Question 26

An analyst is assigned a blind quality control sample of blood containing a drug metabolite. He tests ten separate portions and obtains the following data for the concentration in ug/mL:
25.2
24.8
26.6
27.0
24.0
26.0
25.5
26.3
24.9
23.9
The accepted true value of this sample is 24.7 ug/mL. What is the % error between the mean obtained by the analyst and the accepted true value? Report to two significant figures

A) 2.9
B) -2.9
C) 4.2
D) -4.2
E) None of the above

Question 27

An analyst is assigned a blind quality control sample of blood containing a drug metabolite. He tests ten separate portions and obtains the following data for the concentration in ug/mL:
25.2
24.8
26.6
27.0
24.0
26.0
25.5
26.3
24.9
23.9
The student t value for 10 samples, nine degrees of freedom is 2.262. Using the sample standard deviation for this data set, what is the ± value of the 95% confidence interval? Report to two decimal places

A) 0.72
B) 0.80
C) 0.76
D) 0.62

Question 28

Suppose an analyst analyzes five samples from a brick of cocaine and reports the %purity using the 95% confidence interval as 50.75% 1.33%
This result is best interpreted as meaning that

A) There is a 5% probability that the true value and the experimentally determined value are the same
B) If the analysis is repeated under the same conditions, 95% of the time, the result will fall into this range
C) There is a 95% probability that the true value is within this range
D) The odds that the true value are in this range are one-in-20
E) I am 95% confident that I do not know the answer

Question 29

An analytical balance is out of calibration and as a result, reports weights that are always 0.15 mg too low. This is an example of

A) Systematic error
B) Random error
C) Precision
D) Reproducibility

Question 30

Random errors are typically

A) Equally positive and negative
B) Inescapable
C) Small in magnitude
D) All of the above
E) None of the above

Question 31

If the null hypothesis is rejected and this is a mistake, this results in a

A) Type I error
B) Type II error
C) Type III error
D) Null error