Question 1

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?

Accepted Answer

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

Question 2

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

Accepted Answer

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

Question 3

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.

Accepted Answer

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

Question 4

Random errors are typically

Accepted Answer

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

Question 5

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

Accepted Answer

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

Question 6

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?

Accepted Answer

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

Question 7

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

Accepted Answer

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

Question 8

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

Accepted Answer

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 
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 9

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

Accepted Answer

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. 
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 10

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

Accepted Answer

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 
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 11

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

Accepted Answer

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

Question 12

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.

Accepted Answer

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

Question 13

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

Accepted Answer

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

Question 14

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.

Accepted Answer

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

Question 15

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

Accepted Answer

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

Question 16

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?

Accepted Answer

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

Question 17

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

Accepted Answer

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

Question 18

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

Accepted Answer

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 
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 19

The NUSAP system

Accepted Answer

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 
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 20

The term uncertainty in forensic chemistry refers to

Accepted Answer

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 
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

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 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.

Random errors are typically

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?

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

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

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

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

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

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

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

The NUSAP system

The term uncertainty in forensic chemistry refers to

Assuring Good Measurements

Chemical Fundamentals

Chromatography and Mass Spectrometry

Spectroscopy

Overview of Drug Analysis

Novel Psychoactive Substances

Fundamentals of Toxicology

Applications of Forensic Toxicology

Overview of Combustion Chemistry

Fire Investigation and Fire Debris Analysis

Explosives

Firearms and Firearms Discharge Residue

Forensic Chemistry and Trace Evidence Analysis

Filters

Exam 1: Making Good Measurements

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 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.

Random errors are typically

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?

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

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

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

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

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

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

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

The NUSAP system

The term uncertainty in forensic chemistry refers to

Assuring Good Measurements

Chemical Fundamentals

Chromatography and Mass Spectrometry

Spectroscopy

Overview of Drug Analysis

Novel Psychoactive Substances

Fundamentals of Toxicology

Applications of Forensic Toxicology

Overview of Combustion Chemistry

Fire Investigation and Fire Debris Analysis

Explosives

Firearms and Firearms Discharge Residue

Forensic Chemistry and Trace Evidence Analysis

Filters