Extrapolation and Radiation

1. (4pts) Which of the following comprise significant portions of the U.S. annual average background exposures to ionizing radiation (ÒsignificantÓ is more than 2% of U.S. annual average)? MTF



A) cosmic rays

D) microwave ovens

F) rocks and soil

B) radon

E) elements inside your body (potassium)

G) gamma rays from processed foods

C) hairdryers and other

household appliances

 

2. (4pts) MTF Bruce Ames has argued that the rodent model of carcinogenesis (cancer testing of chemicals using rodents) may have serious flaws. That challenge is based on a possibly faulty

A)   extrapolation across species (rodents to humans)

B)    extrapolation across doses

C)    extrapolation across related hazards, or

D)   AmesÕs challenge is not related to an extrapolation at all

 

3. (4pts) Which examples/options fit either an accelerating or threshold model of extrapolation? In this question, you are simply deciding if the extrapolation is greater than linear in some fashion. MTF

A)   Considering your accident rate when driving after no drinks as a baseline, you are 4X as likely to have an accident while driving after two drinks as after one drink

B)    If AT&T can save $2 billion by laying off 20% of its workers, it can save $10 billion by laying off 100%

C)    Half the LD50 dose of radiation kills less than 25% of animals (the LD50 kills half).

D)   A company needs to sell 1,000 products to break even (no profit) but the profit per product increases with each additional product sold.

 

4 (4pts). MTF The advice given to Austin residents (circa 1985) to avoid eating more than one fish a week from Town Lake was based on a concern that fish had high doses of chlordane levels (chlordane was a pesticide used in termite treatment). The advice that Òeating one fish per week is OK but eating 2 or more per week is not OKÓ involves

A)   extrapolation across species (fish to humans)

B)    extrapolation across doses

C)    extrapolation across related hazards

D)   a linear extrapolation

Errors in Data

5. (4pts) Winning rates at the slot machines at two different casinos are compared for a single day. There is some difference in the average rate between the casinos. Data are then collected for a month of winnings, and the difference between the two casinos is greatly reduced. What type of error underlies most of the differences in daily winning rates between the casinos? One answer only.

A) Sampling        B) Bias         C) RPA                        D) Human and technical                       E) None

 

6. (4pts) The company running the Lotto advertises winners to convey the impression that anyone can be a winner too. However, only winners are shown in these ads, even though winners comprise a tiny fraction of all players. Thus the difference in the incidence of winners shown in the ad is consistently much higher than the real incidence of winners. Assuming that you can treat this difference as a type of error, what type of error is this? One answer only.

A) Sampling        B) Bias         C) RPA                        D) Human and technical                       E) None

 

7. (4pts) You are asked to guess the number of pennies in a large jar for a prize, the only stipulation being that you cannot directly count them in any fashion. Using a scale whose accuracy has been confirmed with standard weights, you weigh the entire bulk of pennies at 4236.74 grams and you weigh a single penny at 2.35 grams (your scale only goes to 2 decimal places). Dividing, you arrive at 1802.86 pennies in the jar, and you round it up to 1803. However, the actual number of pennies is actually 1800, and you donÕt win the prize. What type of error is responsible for your miscount? One answer only

A) Sampling        B) Bias         C) RPA                        D) Human and technical                       E) None

 

8. (4pts) Which in the following list constitute(s) human and technical error? MTF

A)   sample mixup

B)    lab protocols fail to work as claimed

C)    outliers of natural variation

D)   failure to follow protocol

E)    deliberate contamination of a sample

Ideal Data (Fixes and error)

9. (4 pts) Which of the following options correctly describe how a classroom demonstration was used to illustrate properties of error? MTF

A)    coin flip to illustrate sampling error and how to reduce sampling error

B)    Òchoose a random odd numberÓ to illustrate unintentional bias

C)    width of a dime to illustrate human and technical error

D)    memory test to illustrate accuracy (as a type of RPA error)

 

(10-11). For each of the following statements, mark the appropriate letters that describe the data design features present. Mark a data feature only if it is explicitly present at some level in the problem description.

 

10. (4pts). You decide to test whether sober people can routinely pass the SFST, and whether age affects performance. You recruit 200 people of different ages and inform them only that they will be given the SFST, they must be sober at the time (verified with a breathalyzer test that is calibrated against a blank), and that you are interested in whether men are better than women at passing the test; they are not told about your interest in the effect of age. They are asked to show up in alphabetical order on the same day. The test is administered by officers in uniform that are certified to administer the test and who follow formal test procedures, the actual trials are video taped and verified by others who are also certified. MTF

 

 

(A) explicit protocol

(C) standards

(E) blind

(B) replication

(D) random

(F) none

 

11. (4 pts) A police group decides to determine how gullible the public is to scams. Hundreds of people are sent invitations to seminars about how to obtain government subsidies (Òfree moneyÓ) for home improvement; of course, no mention is made in this invitation about the real purpose. Each person is invited to only one seminar, but different people are invited to different seminars, so that the police group can try different scamming methods and see which are the most effective. Approximately 50% of the invitees attend their seminar, where they are encouraged to provide the seminar organizers with social security numbers, bank account numbers, and other data that a con artist could use. The attendees are then informed of their vulnerability to scams. Which features are indicated? MTF

(A) explicit protocol

(C) standards

(E) blind

(B) replication

(D) random

(F) none

12. (4pts) MTF A standard (measurement control) to evaluate whether a DNA typing lab is making mistakes could consist of which of the following. Assume that the DNA type (barcode) of the sample is unknown to you unless indicated otherwise. ÒCodedÓ means that a number is attached to the sample but without the name of the person whose DNA it is; ÒlabeledÓ means that the sample is labeled in some fashion which may or may not be coded. Assume that you are the one sending the standards to the lab for testing. You want to know if the results could possibly tell you if a mistake has been made without further testing on your part. A standard in this case is

A)   a sample whose DNA type/barcode is known to you in advance

B)    a coded sample of DNA

C)    two samples of the same DNA that you have labeled differently but you know are the same

D)   any labeled sample of DNA

E)    any replicated sample of DNA (two samples from the same person)

13. (4pts) Don polled two groups of people for their opinions on the Iraq war. One group consisted of 200 UT students passing by the Student Union one day; the other group consisted of 100 people in a much larger audience attending a Baptist sermon on Sunday. Attitudes were substantially different between the two groups. Don wants to rule out the possibility of bias instead of sampling error as the cause of the difference. What options describe reasonable ways to decide if his observed differences are due to sampling error rather than bias? MTF

A)   Obtain a third sample different from either of the first two groups (from non-students, non-churchgoers). If that third sample matches either of his first two samples, or if it falls between them, then he can be confident that the difference among his first two is sampling error.

B)    Obtain much larger samples from the two original groups (a larger sample of UT students, a larger sample of people attending the same church); if the difference persists, he can be confident that the difference is not sampling error.

C)    Perform a statistical analysis of the data; a statistical analysis will tell him whether the differences are consistent with sampling error.

D)   Repeat the surveys with new people at the same locations but using a different set of questions. If the original difference was due to bias rather than sampling error, the bias should go away when the questions are changed.

.

14. (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.

 

 

15. (4pts) 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. MTF

A)   error: sample mixup. Fix: code tubes blindly

B)    error: unintentional failure to follow protocol because it is difficult to understand. Fix: design a protocol that is easier to understand but achieves the same objectives

C)    error: lab fails to conduct analyses carefully and fails to check results because they know which samples belong to the suspect and know what results are consistent with suspect being guilty. Fix: code samples so that lab does not know which belong to suspect.

D)   error: lab occasionally declares false matches, but they often go undetected. Fix: blind proficiency tests to measure the error rate.

(16, 17). 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 from the lab's perspective. 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. New: a parentheses ( ) around a blood type, marker or gender 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)

Darin Rokyta

Darin Rokyta

(AB)

(Male)

(negative)

(C)

Rachael Springman

Rachael Springman

O

Female

+

(D)

#132

Darin Rokyta

(AB)

(Male)

(negative)

(E)

#218

Patsy Cline

(A)

Female

(+)

(F)

#10

Pam Hines

O

Female

negative

(G)

Jerry Allison

Jerry Allison

B

Male

negative

(H)

#101

Brent Iverson

AB

Male

negative

(I)

No combination of tubes can satisfy the protocol

 

 

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).

 

16. (3 pts) Choose two tubes to achieve replication of gender but nothing else. You should know both that gender 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)

 

17. (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)

 

 

 

18 (5 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. MTF

 

 

(A)   There is greater bias in the left graph, because the left shows that more people failed to get the right proportion of heads.

(B)   Classes from different years have generated different distributions of the proportion of heads

(C)   Replication reduces sampling error

(D)   The right graph has the least RPA error.

(E)   With 10 flips, most of the class failed to get within 5% of the expected frequency (50% heads)

(F)    Pooling the data from the entire class (and previous classes) consistently yielded results close to 50% heads (within 5% or so)

(G)   Bias and sampling error can affect the same data

 

 

Drug Testing, DWI testing

           

19. ( 4 pts). What constitutes 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

E)    A proficiency test given to the lab that does the analysis, regardless of whether the test is blind.

 

20. (4pts) Which protocol features are not needed or important when drug testing (e.g., to test for the presence of cocaine) but are needed or important for DNA typing and determining the significance of a match? Options are correct if they identify something is specifically useful only for DNA type matching. MTF

A)   replication

B)    a knowledge of lab error rates

C)    standards in the form of a sample of known properties

D)   methods to calculate a RMP

E)    blind processing of samples

F)    a reference database from the human population

 

21. (4pts) What described in class or book constitutes a form of replication in DWI testing? To be correct, the option must both describe replication and be something that is actually done or used. MTF

A)   multiple air blanks in the breathalyzer test

B)    multiple breath samples from the suspect

C)    an air blank plus the breath sample from the suspect

D)   multiple tests used to assess SFST performance

E)    a sample of known alcohol content tested by the breathalyzer

F)    an explicit protocol (formal procedure) for giving SFST instructions to the suspect

 

DNA Typing plus Criminal Justice System

 

22 (4 pts). The goal is to determine lab human and technical error rates of DNA typing through replicated typing of the same individuals. Ten tubes whose DNA type is unknown are sent to the lab. These 10 samples are from 8 people, but the lab does not know the number of people. Different tubes from the same person have different codes. For this goal, is the replication blind to the lab performing the typing? Why or why not? MTF

A)   It is blind, because the lab does not know which tubes belong to the same person.

B)    It is not blind regardless of the labels, because the lab can figure out which samples are the same after they do the DNA typing.

C)    It is ambiguous as to whether the procedure is blind, because there are ways in which the procedure is blind and other ways in which it is not.

D)   It is not blind because there is no standard sent with the tubes.

23-25 (3 pts each). Fill in the blanks of the ÒconsequencesÓ column of the table with the best option(s) from the list below the table. The question number is given in each blank.

 

Deviation from Ideal Data

Consequences

lack of replication

23. one answer only

samples not processed blindly

24. MTF

Inadequate protocols for analysis of results

25. one answer only

Your choices for consequences are:

(A) Improper calculation of RMP (random match probability) in some cases

(B) Sample mix-ups in a case can go undetected

(C) The RMP threshold for conviction will appear to be exceeded when it is actually not exceeded

(D) Allows deliberate contamination of sample

(E) This protocol is no longer applicable because of recent changes in DNA typing methods

(F) The protocol allows for a biased willingness to accept results

(G) Selective reinforcement of the prime suspect

(H) The protocol increases the likelihood of sample mix-up

(I) The full extent of lab error rates remains unknown

(J) This protocol allows outliers of natural variation to escape detection

 

26. (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.

 

 

27. (4pts) Considering the last two decades, which forensic methods have been shown (in proficiency tests) to have error rates sometimes exceeding 10% or to otherwise be unreliable? MTF

 

A) polygraph (lie detector)

D) hair matching (not DNA based)

B) fingerprint matching

E) eyewitness identification

C) DNA typing

 

 

 

 

 

 

28. (4 pts.) Exam Key Code: Fill in (AB) on question 28 to indicate your exam code.

Also, fill in the correct bubbles for your name and pad number 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.