Exam 1, Biology 301C, 14 September 1998

Language of evaluation

1-3) (3 pts each) We wish to test the model that the incidence of gonorrhea declines after beer taxes are raised. For the following possible data, which consequences (A, B, C) apply? Note that this question is not about causation versus correlation, only about data and a model that happens to describe a correlation. (MTF)

A) The data are inconsistent with the model

B) The data are irrelevant to the model

C) The data support the model

1) Data: 20 spins on a roulette wheel, 15 are Red A B C

2) Data: In two separate instances, the incidence of hepatitis B infections was unchanged after beer taxes were raised. (Hepatitis B is not gonorrhea.) A B C

3) Data: In two separate instances, the incidence of gonorrhea was unchanged after beer taxes were raised. A B C

4) (12 pts) The following points pertain to the book and lecture on evaluation. Which statements are true? (MTF).

(A) Data are considered inconsistent with models because all models are false.

(B) Classifying data as irrelevant to a model means that the data could not possibly refute it no matter how they turned out.

(C) Classifying data as irrelevant to a model means that the data were not gathered according to the Ideal Data template.

(D) In considering guilt versus innocence of a suspect in a crime, the law specifies that we adopt the view that the suspect is considered innocent until proven guilty (consider this statement true). The model of innocence is an example of a null model because it is the model we accept until evidence forces us to reject it.

(E) In science and in many aspects of society, our willingness to reject a null model increases as evidence accumulates against that model. For example, in class, our acceptance of the safety of a vaccine (against the null model that the vaccine was not safe) increased as the sample of successful trials increased.

(F) In a Pepsi versus Coca-Cola taste test, one would use either null model that Pepsi tastes best or that Coca-Cola tastes best.

(G) By definition, once a model has been accepted, that model cannot be refuted in further tests.

(H) The criteria for acceptance of a model are rigid in science and society, and there is little legitimate room for disagreement as to whether a model should be accepted or not.

(I) A null model is part of every properly designed study. If the study does not have a null model, then it is not properly designed.

Correlations

5) (6 pts) We considered the correlation that people living in cities/towns with high fluoride in the water supply have low tooth decay rates compared to people living in towns with low fluoride (fluoride level is variable X, tooth decay rate is variable Y). Which of the following causal models of this correlation use a “third variable” to explain the correlation (meaning that X and Y are not causally related)? MTF

Causal model	Cause invoke a third variable?
high fluoride makes teeth tougher against the agents causing tooth decay	Fill in 5 (A) if a 3^rd variable is invoked
water supplies with high fluoride also have high magnesium, and it is the magnesium responsible for low tooth decay	Fill in 5 (B) if a 3^rd variable is invoked
people living in areas of high fluoride have higher incomes and can afford better dental hygiene; better dental hygiene is what lowers tooth decay.	Fill in 5 (C) if a 3^rd variable is invoked
high fluoride kills the bacteria in the mouth that cause tooth decay	Fill in 5 (D) if a 3^rd variable is invoked

6-8. (3 points each) Researchers have discovered that HIV (the AIDS virus) is more frequently transmitted heterosexually (vaginal intercourse) in Africa than in North America, where it is chiefly transmitted homosexually. They have also discovered that circumcision is at a much lower incidence in Africa than in North America. They have thus proposed that circumcision is a way of reducing the spread of HIV.

Use the following variables:

Variable 1: continent

Variable 2: incidence of heterosexual HIV transmission

Variable 3: incidence of circumcision

For each of the following questions, you are given a pair of these variables. You are asked to choose among the following 3 options that best characterizes their relationship in the problem description above.

(A) no correlation or causation is indicated.

(B) a correlation is indicated, but no causation between the variables is suggested

For each pair of variables given below, which option applies (one answer each)?

6. Variables 1 & 2: (A) (B) (C)

7. Variables 1 & 3: (A) (B) (C)

8.Variables 2 & 3: (A) (B) (C)

9) (5pts) Again consider a correlation between fluoride and low tooth decay rates. If magnesium (not fluoride) in drinking water is the true cause of low tooth decay rates, which tooth decay rates are expected in cells 1 & 2 of the following table? Assume that no other variables besides fluoride and magnesium are important. (one answer only)

		Magnesium:
		present	absent
fluoride:	present	low decay	(1)
fluoride:	absent	(2)	high decay

A) 1 is high, 2 is high	C) 1 is low, 2 is high
B) 1 is high, 2 is low	D) 1 is low, 2 is low

10. (5 pts; hard; options have changed) New diagnostic methods have allowed us to detect cancers at earlier ages than in the past, and the average age of a person first diagnosed with cancer has decreased. In addition, people have been living longer from the times of their diagnosis. That is, if A is the average age of a person when cancer is diagnosed and Y is the number of years a person lives beyond diagnosis, there is a (negative) correlation between A and Y (Y increases as A decreases). Note that the average age of death of a diagnosed person is A+Y. Which of the following models are consistent with this correlation? That is, which models are not rejected by this correlation? MTF

(A) There has been no change in the age at which people diagnosed with cancer die.

(B) There has been no change in the number of years a person lives beyond their diagnosis of cancer.

(D) Early diagnosis causes a person to live to a later age than does late diagnosis.

Electromagnetic Fields

11. (5 pts) Scientists currently accept which of the following models about EMFs? (It is of course possible that a model which is supported now may be rejected in the future.) MTF

(A) Most of the available data concerning EMFs and cancer are correlational

(B) If residential EMFs from power lines and transformers do cause leukemia, they increase risk by less than a factor of 2.

(D) Gamma rays are a major source of the low-frequency EMFs that US citizens receive.

(E) The intensity (strength or "brightness) of an EMF falls off quickly as one moves away from the source of the field

Controls

12. (6 pts) Each of rows (A)-(G) describe different treatments that could be applied to humans in generating data on heart disease. The treatments differ in which factors are present (indicated by “+”) or absent (-). Factor 1 is the use of a cholesterol-lowering drug (statins); factor 2 is a diet low in saturated fat; factor 3 is moderate exercise; factor 4 is a diet with daily fish oil; factor 5 is one ounce per day of alcohol.

Which two treatments would you want to compare to determine if factor 1 is correlated with differences in heart disease when all other factors are controlled? In evaluating possible answers, pick any comparison that controls for all unwanted factors, and assume that these treatments differ only in the ways stated. Mark exactly two options, or none if none apply. Each row (each option) describes a different set of conditions, so to know which factors would be applied in a treatment, you look across the row. If multiple combinations satisfy the problem, any correct combination will be accepted. (Two answers or None; options have changed).

	factor
Option		1	2	3	4	5
	(A)	-	+	+	+	+
	(B)	-	+	-	+	-
	(C)	+	+	+	-	+
	(D)	-	-	+	+	-
	(E)	+	-	-	-	-
	(F)	+	-	+	-	+
	(G)	+	+	-	+	-

13. (6 pts) Mark all of the following statements about controls that are correct. MTF

(A) Controls are present in any (defined) correlation, whether the correlation is zero, negative, or positive.

(B) A control establishes a baseline.

(C) In the video comparing human and penguin intelligence, the last stage of the IQ test controlled for environmental and language differences.

(D) In the video comparing human and penguin intelligence, brain size was not considered a good model of intelligence because there was no way to control for differences in body size between penguins and humans.

(E) The choice of subjects both blindly and randomly guarantees that a control is present.

(F) One of our themes is that experiments make the best controls. What this theme means, in part, is that a test cannot be considered an experiment unless it has a control group.

(G) To control for factor X, X must be absent in all study groups

14. (6 pts) An epidemiologist does a survey to evaluate whether a person’s tendency to acquire a criminal habit later in life can be predicted from characteristics of their environment early in life. Only correlational data are gathered (no experiment). For such a study, which of the following options are true? MTF

A) Characteristics that are the same for all individuals in the study (e.g., country of residence, if the study was confined to one country) would not be controlled for because they are not variables in the study.

B) Variables that were not recorded about each individual in the study could not knowingly be controlled for.

C) Variables that were recorded about each individual in the study could be analyzed so that they were controlled for.

D) Suppose the goal was to assess whether the childhood neighborhood was a factor in development of a criminal habit. If four different neighborhoods were chosen for the study, then the random choice of which individuals within each of those neighborhoods to include in the study would ensure that all variables besides neighborhood would be controlled (on average).

Experiments

15. (4pts) The test of FC shown in the video was an experiment because (one only)

A) it included controls	C) it manipulated the normal FC environment	E) all of the above (A-D)
B) it was blind	D) it included several levels of replication

16. (6 pts) On-line survey and/or video of horoscope experiment. Which of the following options apply to the on-line survey given to the class and/or the horoscope experiment, as shown or discussed in lecture? MTF

A) Randomization. In light of the goal, the study would have been improved if the distribution of who got which survey had been randomized, both in our class and in the video.

B) Blind was essential to the goal of the studies. If everyone had known the true purpose of the survey (and had known the design), it is likely that our class and the one shown would not have rated the personality description so highly.

C) Replication. Similar outcomes have been obtained in previous years of Bio301D. Furthermore, essentially the same outcome of positive responses was shown in the video.

D) Controls. It is ambiguous whether controls were present in the video.

In the following questions, consider italicized phrases and sentences as true.

17. (6 pts) Prisoners of Silence (Facilitated Communication, or FC). Which of the following options either depict what was shown in the video, or correctly explains the nature of the study done in the video? If any part of an option is incorrect, consider the option incorrect and do not mark it. MTF.

(A) Model tested: the video showed that allegations of sexual abuse had been typed by autistic children when assisted by their facilitator. The model tested in the video was that the autistic child was not being truthful about the sexual abuse.

(B) The need for an experiment. In the normal FC environment, the Facilitator knew what answer was expected. This was the basic problem that required an experimental test to determine whether the communications were real.

(C) Evaluation of results: the video showed several people who interpreted the outcome of the tests as evidence that FC does not represent communication by the child. A legitimate criticism of these tests and of that interpretation is that the child was intimidated by the test environment and, consequently, could not perform well when being tested.

(D) Blind: Blind was an essential feature of the design. That is, the goal of the experiment required at least that the Facilitator not know what the child was being asked.

18. (5 pts) This question refers to the palm-reading segment shown in the "Secrets of the Psychics" video. Which statements about models and design features are true? Ray Hayman was the palm reader. MTF

A) Ray had been a skeptic of palm reading throughout his college years, and he designed palm reading experiments to convince others it was bogus.

B) Ray’s palm reading experiments were done on photographs of hands, and his readings were transcribed and given to the people for evaluation.

C) The controls for his experiments were people given the written description of readings done on pictures of their own hands; the treatments were people given the written description of readings done on pictures of hands from other people.

D) There are explicit (written) protocols for palm reading that Ray had used to teach himself the proper technique.

One more page ...
Standardized Field Sobriety Tests (SFST)

19. (12 pts) Which of the following options are true about the SFST lectures? MTF

A) There are specific protocols for conducting the SFST. These protocols describe how to give instructions to perform the test as well as how to evaluate the performance.

B) Class discussed 3 different tests in the SFST: Walk and Turn, Horizontal Gaze Nystagmus, and One Leg Stand.

C) Baseline data indicate that a sober person fails any one of the 3 tests only 5% of the time. The failure rate is slightly higher for people over 50 than for people under 50.

D) There have been “validation” studies showing that officers in the field (on duty, encountering drivers as they normally do) can use the SFST to reliably assess whether a driver exceeds the 0.08% blood alcohol limit approximately 90% of the time.

E) The validation studies done in the field have been blind in the sense that the officer performing the SFST did not know the blood alcohol content of the driver but have been non-blind in the sense that the officer knew that an observer was recording the officer’s conduct of the test.

F) A graph showed that the number of highway deaths per million vehicle miles has declined over the last 40 years. It was also shown that SFST use and DWI arrests were implemented about halfway during this 40-year period and that the rate of highway deaths continued to decline after this implementation. The cause of this decline in highway death rate is therefore at least in part due to the implementation of SFST and DWI arrests.

G) The scoring of the SFST is somewhat arbitrary because some deviations are not always clear-cut.

H) If you score 2 points or more on any of the 3 SFSTs, the officer is obliged to arrest you.

I) Starting either the WAT and OLS test before instructed to do so is scored against you.

J) Texas law allows you to be arrested for driving under the influence only if your blood alcohol content exceeds 0.08% or if your performance on the SFST indicates your are over this limit.

K) The fact that you blow much less than 0.08% on a breathalyzer will not necessarily be grounds for releasing you, because it is commonly assumed that drivers with low blood-alcohol are under the influence of other drugs. However, direct evidence of these “other” drugs is often not sought by the government.

20. (5pts) Key code, name, and pad number. Fill in (A B) on scantron field 20 to indicate your key for this version of the exam. Be sure your name and pad number are correctly bubbled in on the scantron and that your name is on this exam form. If your name is not on this copy as well as the scantron form, you can be penalized 40 points, if we can even determine that you took the test.

Causal model

Cause invoke a third variable?