Extrapolation (Models)
1. (4pts) Class and the book described 5
examples of extrapolation, listed below.
For which of those was the extrapolation eventually replaced by
observations suggesting that the original extrapolation was incorrect? MTF
A)
a
chemicalÕs maximum exposure threshold at 1 millionth of the LD50 dose in a
suitable rodent model
B)
fetal
alcohol syndrome
C)
rodent
models of cancer
D)
risk
of second-hand tobacco smoke
2. (3pts). Four graphs of extrapolation were
illustrated in lecture and the book. To which types of extrapolation do the graphs apply? MTF
A)
extrapolation
across species (fish to humans)
B)
extrapolation
across doses
C)
extrapolation
across related hazards
Errors in Data
3. (4pts) Two samples of
opinion from the same student body differ but the difference is not
statistically significant. To what
type of error do we attribute the difference? One answer only.
A) Sampling B)
Bias C)
RPA D)
Human and technical E)
None
4. (4pts) Pre-election polls often use a particular medium for contacting
people (e.g., landline phones).
Although polls typically involve thousands of participants, and multiple
polls are taken, their results often differ by large margins and in the same
direction from the election results.
What type of error accounts for the difference between voter opinions
measured by polls and the voter opinions in the actual election? One answer only.
A) Sampling B)
Bias C)
RPA D)
Human and technical E)
None
5. (4 pts) Charmin advertises 500 sheets of toilet paper per roll. A competitor decides to check out the
claim, but instead of counting the sheets, takes the following shortcut. The competitor measures the length of 5
sheets to the nearest 1/6 inch, multiplies it by 100 and compares it to the
length of the entire roll. The
entire roll comes out 7 inches short of the calculated length for 500 sheets,
and a single sheet is 4 inches long.
The competitor thus claims fraudulent advertising by Charmin, but an actual count reveals that
there were indeed 500 sheets in the roll. What type of error accounts for the difference between the
calculated number of sheets and the actual number of sheets? (one answer
only)
A) Sampling B)
Bias C)
RPA D)
Human and technical E)
None
6. (4 pts) A survey of
several hundred men and women between the ages of 20 and 40 finds that 4/5 of
women do not like to spend Sunday watching football, whereas half the men do
prefer this activity. The
difference is observed in a follow-up survey. What type of data error is indicated by the consistent difference
between the sexes in preference for watching football on Sunday? (one answer
only)
A) Sampling B)
Bias C)
RPA D)
Human and technical E)
None
7. (5 pts) A customer complains that prices charged at the Far West HEB
grocery store are often different than the advertised prices, and further
suggests that the difference often goes in favor of the store (the charged
price is usually higher than the advertised price). The store does an audit of all 2630 items it sells
and finds that there are several items marked differently than charged. A distribution of the differences is
shown below;
the center bar at 0
represents items for which the charged price was the same as the advertised
price;
bars to the left of center
are items in which charged price was more than advertised,
bars to the right are those in which the charged
price was less than advertised.
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Which options fairly describe the data and the customer
complaints? MTF
A)
The
suggestion that the store usually charges more than advertised is a claim that
the price differences are biased.
B)
The
distribution shown clearly supports a claim of bias against customers because
of the tall bar to left of center (at Ð1).
C)
The
distribution shown clearly supports a claim of bias in favor of customers
because of the tall bar to right of center (at +1).
D)
The
study cannot assess bias because the 2630 items were not chosen randomly.
Ideal Data : Fixes
8. (4pts) In which of the following studies
would the protocol need to include a design feature to ensure that subjects
are blinded to
avoid bias? Do not choose any
options in which a blind design feature would not be possible or would not be
necessary. All options describe
the subjects (underlined) as well as the purpose of the study. MTF
A)
Rats
fed a substance to see if it causes cancer in them.
B)
Humans
accidentally exposed to a high dose of a chemical now being observed because
they fear its possible toxic effects.
C)
Students
filling out a form graded by a machine to test whether they respond favorably
to a scam.
D)
Different
car repair shops in Austin being evaluated by an independent agency to
find out if they treat the average customer fairly.
9. - 11 (3
pts each) In the
following table, fill in the appropriate ÔfixesÕ for each type of error. A fix may merely enable you to detect
the error. MTF
Error |
ÔFixÕ
|
Sampling |
9. (A) replication (B)
random (C)
blind (D)
standards |
Bias |
10. (A)
replication (B)
random (C)
blind (D)
standards |
Human and technical |
11. (A)
replication (B)
random (C)
blind (D)
standards |
(12,
13). For each of the following statements, mark the
appropriate letters that describe the features present. Mark a data feature
only if it is explicitly present at some level in the problem description.
12. (4pts). An
instructor gives two exams during the first part of the semester. Both exams are on Wednesday, as has
been the policy in the past. The
class complains that Monday exams would lead to higher scores, on the grounds
that students are more rested and have more time to study immediately before
Mondays. The instructor bows to
class pressure and gives the next two exams on Mondays. The scores are not higher than for the
first two exams, so the instructor concludes that the day of an exam makes no
difference. MTF
(A) explicit protocol |
(C) standards |
(E) blind |
(B) replication |
(D) random |
(F) none |
13. (4pts) You are hired as a consultant for a company selling home
pregnancy tests to help them market a product that will be easy to use and give
accurate results. You advise them
to put a picture of a woman on the front of the box and directions for use on
the back. Furthermore you suggest
that they provide supplies for just a single test, so that if a woman wants to
test herself again, she has to purchase a second kit. Finally you suggest that they include a sample solution in
the kit that will provide a definite positive result that can be used if the
woman tests negative. Which
aspects of the ideal data template would be satisfied by a single kit if your
recommendations are followed? MTF
(A) explicit protocol |
(C)
standards |
(E) blind |
(B)
replication |
(D)
random |
(F) none |
14 (4 pts). The following pair of graphs was
shown in relation to the coin flip demo in class. Which points were illustrated by either or both graphs? The horizontal axis is the proportion
heads, and both horizontal axes span 0 to 1. The left graph is based on 10 flips per observation, the
right is based on over 1000 per observation. MTF
|
|
(A)
The
left graph exhibits considerable RPA error, because the average proportion of
heads inaccurately matches the observed number of people who got 50%
heads.
(B)
The
left graph shows more replication (more coin flips) because there are more bars
in the graph than in the right graph
(C)
Sampling
error reduces bias
(D)
The
right graph has the least sampling error.
(E)
With
10 flips per student, most of the class failed to get within 5% of the expected
frequency (50% heads)
(F)
The
left graph has more bias than the right because it has more observations well
outside of 50%
(15, 16). Do-it-yourself protocol. You are
conducting an external review/test of a genotyping lab. Your job is to send two tubes to the lab, with labels. There are
several options for the content of and label on a tube. You must decide which
contents to send and how to label the tubes so that the features of ideal data
requested in the question are present. If a tube has a person's name on it, the
lab can assume that the tube contents belong to the name of the person on the
label. If a tube is labeled with a number, the contents are unknown to the lab
but known to you. A ? indicates that you do not know the individualÕs status
for that characteristic. Your options for tube contents and
tube labels are:
option |
tube label |
Contents in the tube
are from |
Blood type
|
Gender |
Marker status |
(A) |
Laura Baker |
Laura Baker |
B |
Female |
+ |
(B) |
Harry Wichman |
Harry Wichman |
A |
Male |
? |
(C) |
Rachael Springman |
Rachael Springman |
AB |
Female |
+ |
(D) |
#132 |
Harry Wichman |
A |
Male |
? |
(E) |
#218 |
Patsy Cline |
A |
Female |
+ |
(F) |
#10 |
Pam Hines |
O |
Female |
negative |
(G) |
Jerry Allison |
Jerry Allison |
A |
Male |
+ |
(H) |
#101 |
Brent Iverson |
AB |
Male |
? |
(I) |
No combination of tubes can
satisfy the protocol |
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In the
following questions, choose two letters among options (A)-(H) to describe the
two tubes that will be sent to the lab. The tube labels are the only
information the lab receives about the samples, and the lab does not have prior
information about the individuals. If it is
possible to satisfy the protocol, the question will require exactly two
letters and only
two letters -- one
for each tube. Thus, the answer for a question might be (A) & (B), or it
might be (D) & (F). If more than one pair of options are possible correct
answers, fill in only one correct pair of options. Thus, if (A) & (B) is
one acceptable answer, and (C) & (D) is another acceptable answer, fill in
either (A)&(B) or (C)&(D), but not both.
If a factor (such as identity, blood type, gender, etc.) is not specified
in the protocol, then that factor will be ignored in grading the answer.
Alternatively, if a protocol cannot be satisfied with two from (A)-(H), fill in
(I).
15. (3 pts) Choose two tubes to achieve replication
of blood type but nothing else.
You should know both that blood type is replicated and that nothing else
is replicated, and the replication should be blind to the lab (you can
assume the lab will know gender from the name on the tube).
two tubes or I: (A) (B) (C) (D) (E) (F) (G) (H) (I)
16. (3 pts) Make the tubes replicated for
marker, gender and blood type, but all replication is blind to the
lab. You should know that the
replication is present, even if you donÕt know the marker, gender, and blood
type.
two tubes or I: (A) (B) (C) (D) (E) (F) (G) (H) (I)
17. (5pts) Which options identify a ÒfixÓ for the type of error
indicated; a ÒfixÓ may either reduce that error or at least allow you to detect/measure that error in at
least some cases. MTF
A)
error: sample mix-up. Fix: split the samples before testing;
have each tested separately; look for discrepancies
B)
error: the lab deliberately creates ÔdataÕ
that they think the prosecution wants. Fix: send requests to the lab blinded, so that the lab cannot
discern what the prosecution wants
C)
error: the RMP is calculated improperly due to
inadequate protocol Fix: split samples before testing; have each tested separately;
look for discrepancies
D)
error:
lab occasionally declares
false matches, but they often go undetected. Fix: split the samples before testing; have each tested
separately; look for discrepancies
18 (4pts) Which features of ideal data are mandated (in the
Congressional record) for the Dept of Transportation drug testing program? MTF
A)
replication
B)
standards
C)
blind
D)
explicit
protocol
19. (3
pts). Which of the
following would constitute a standard in a drug test for evaluating lab
error rates? MTF
A)
A
sample with a known level of drug present.
B)
A
sample known to be drug-free.
C)
A
written procedure describing the level of performance to be upheld by the lab
D)
Any
measure taken by the lab to detect or reduce human and technical error
20. (4pts) For a technique used to declare a match between a forensic
sample and a suspect, such as DNA typing, fingerprinting, or hair matching,
what is the consequence of not having a reference database from the
population? MTF
A)
Without
a reference database, it is not possible to conduct proficiency tests of lab
error rates.
B)
Without
a reference database, it is not possible to calculate a RMP (random match
probability)
C)
Without
a reference database, it is not possible to detect sample mixup
D)
Without
a reference database, there is no benefit of blind procedures.
21. (4pts) If the lab declares a match between a suspect and a crime
scene sample, and there is a very small probability of a random match (e.g., 1
in a billion) but a much larger probability that the lab made a mistake and
falsely declared a match (e.g., 1%), what can be said about the odds that
the suspect does not match the sample?
one answer
A)
The
odds are still close to 1/billion because there is a 99% chance that the lab
did NOT make a mistake, so 0.99x1/billion is still close to 1/billion.
B)
The
odds are close to 1%, because 1% of the time the suspect will not match even
though the lab indicates a match, and 1/billion times the match will be because
of a random match. 1% + 1/billion
is close to 1%.
C)
The
odds are 1/billion divided by 1%, hence 1/(10 million)
D)
The
odds cannot be calculated when two types of error are present.
22 (4pts) Which of the following options were said to be ideal
characteristics of a forensic method to identify people? MTF
(A)
The
methods are kept confidential to the lab performing the test
(B)
A
reference database exists
(C)
The
characteristics measured vary continuously, are not discrete
(D)
The
methods and labs are able to pass proficiency tests
(E)
The
method should only be used if it can show that each person is different from
everyone else
23
(4pts) An
eyewitness video was shown in class in which a single young male was
observed. Following that video,
the individuals in the class were asked to identify that person in a
line-up. Which of the following
is/are true as pertains to the purpose or content of that demo? MTF
(A) Bias: the demo showed how subtle clues given
about the nature of the person you saw (height, appearance) could lead you to
identify the wrong person even when the right person is present in the same
line-up.
(B) Bias: the demo showed how instructions about
who may be present in the line-up could influence whether you identify the
wrong person
(C) Bias: the demo showed how the order of
suspects in a line-up matter Ð that you are likely to choose someone in the
middle
(D) Accuracy of
eyewitness ID: at least 1/4 of the
class identified the wrong person
(E)
Replication: both classes
were given the same instructions and choices; the responses were similar except
for possible sampling error
24. (5pts) For which of
the following methods was it said that labs failed proficiency tests or failed
to take proficiency tests (failure rate of at least 10% when tested)? If a method was not mentioned in class,
do not choose it. MTF
(A) fingerprints Pre-1990 |
(C) DNA typing |
(E) bite mark ID |
(G) eyewitness ID |
(B) fingerprints post-2000 |
(D) hair matching (by microscopy, not DNA) |
(F) shoeprint ID |
(H) dog sniffing |
25
(3pts). Which are true of non-DNA
based hair matching?
A)
It
was used in US courts for several years and was a factor in several wrongful
convictions
B)
Proficiency
tests revealed error rates sometimes in excess of 50%
C)
It
has been discredited in the U.S.
D)
There
was no reference database for hair matching
26 (3pts) Which are true about current and past DNA typing
methods? (RMP = random match
probability)
A)
The
DNA typing method that now gives the lowest RMP uses DNA from mitochondria
B)
The
Y-STR method can estimate the number of males in a sample
C)
The
original technology for DNA typing involved visual comparison of an image (as
shown in class)
D)
Current
DNA typing methods were said to satisfy our 4 properties of an ideal
identification method
E)
DNA
suitable for typing can come from small tissue samples, such as the follicle
end of a hair or something you have licked.
27. (3 pts.) Exam Key Code: Fill in bubbles (AB) on question 27
to indicate your exam code; leave the other bubbles blank. Also, fill in the correct bubbles for
your name and EID on the scantron form.
You must turn in this hard copy (with your name on it) and
your scantron to receive credit for this exam.