Biology Case Studies in Multiple-choice Questions

Case Problems in Authentic Assessment

Many educators advocate the use of authentic assessment, which refers to measurement of student performance on tasks that would be expected of a person functioning in society as a citizen or employee.

Authentic assessment has several possible benefits: (1) It focuses educational measurement upon relevant, worthy educational outcomes, (2) it implicitly conveys to students that they are learning valued skills rather than trivia, and (3) the assessment process is value-added, as the assessment can be educative.

One method of improving student assessment in biology is to employ case problems featuring authentic scenarios and data. The use of case problems in test questions forces the instructor to focus on realistic tasks.

Realistic Test Questions

Authentic assessment requires educators to create real rather than contrived activities and to create real contexts for student performance. Written examinations do not strictly qualify as authentic assessment, but in budget-limited freshman college courses they may be a necessary component. Benefits attributable to authentic assessment may be approached by striving for realism in test questions.

• Each test item should resemble a question that could be asked of a person performing in a workplace or as a citizen.

• Test questions should measure a diversity of useful learning outcomes -- application of biology to realistic problems, step-wise cause-effect analysis, problem-solving, data analysis, investigative design, critical thinking and creative thinking.

Realism of Multiple-choice Questions

The authenticity of multiple-choice questions can be maximized by framing each question stem as a case example.

A weakness of multiple-choice questions is their failure to emulate the demands of a workplace in which employees lack access to a fixed list of choices each time a decision is required. Free-response questions, by contrast, require the student to construct a response in the absence of hints or suggestions.

A strength of multiple-choice questions is that they do emulate a workplace in which colleagues or clients put forth an number of hypotheses which must each be understood, considered, and weighed in arriving at a decision.

Validity of Multiple-choice Questions

To what extent could a student who chooses a suitable answer from a list also produce a response of equivalent quality in the absence of choices? Multiple-choice questions do not allow direct measurement of the latter, but they may be valid indices of competency.

Research indicates that a given student is likely to have a similar performance ranking on both multiple-choice tests and tests employing free-response open-ended questions. This may tell us only that intelligent hard-working students do well on exams. Student achievement may be driven by underlying variables such as reading-comprehension and self-discipline. For example, the Whimbey Analytical Skills Inventory is a powerful independent predictor of success in biology.

But there is some direct evidence that multiple-choice items can predict the quality of answers that would be generated in the absence of choices, although this relationship requires validation with each learning outcome. A multiple-choice item might identify with great confidence an ability to perform a complex multi-step calculation in the absence of choices, but caution would be required in determining to what extent multiple choice questions could identify scientific innovators, great public speakers, or superb tennis players.

If multiple-choice questions are the only cost-effective assessment option for instructors with budget-limited marking time, the questions should be employed with these limitations in mind.

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CONSTRUCTING QUESTIONS EMPLOYING CASE PROBLEMS

Concisely-worded examples, such as those shown below, allow testing of basic scientific literacy and fluency with a large number of core concepts and skills.

Subject matter can include any concept deemed worthy of testing, but note that (1) questions are cast in the context of a situation that a real person could encounter, (2) a diversity of learning outcomes is covered, and (3) some questions require that the student invoke a number of skills, concepts, and algorithms in order to construct a suitable answer.

The following examples illustrate a range of responses that might be expected from students given brief statements of realistic case scenarios.

Interpret Meaning:

The sexually-transmitted disease gonorrhea is becoming difficult to treat because the causative bacteria are evolving resistance to antibiotics. For example, in Hawaii between 1997 and 1999 resistance to fluoroquinolones increased from 1.4 percent to 9.5 percent. Scientists attribute this to natural selection. What does natural selection mean in this context?

1. The germs have learned to avoid that particular class of antibiotic.
2. The antibiotic has changed the genetic structure of the germs allowing them to become antibiotic-resistant.
3. The germs changed their genetic code in order to avoid problems with the antibiotic.
4. The antibiotic created an environment in which germs harboring antibiotic-resistant genes could flourish.
5. The mutation rate for antibiotic-resistance increased during the time period.

Interpret Data:

An investigator monitoring physiological parameters in an Olympic athlete in training subjected the athlete to an episode of extreme exercise and found a plasma anion gap of 20 (reference value =12). What is the most likely explanation for this?

1. Protons from lactic acid have reacted with bicarbonate.
2. The plasma lactate ion level has dropped by 8 mmol/L.
3. The plasma hydrogen ion concentration has risen to 20 mmol/L.
4. The plasma bicarbonate ion level has risen by 8 mmol/L.
5. Plasma chloride has risen to 20 mmol/L.

Weigh Hypotheses:

An 18-year-old woman with healthy parents showed muscle weakness. Her brother had been diagnosed with an X-linked recessive muscular dystrophy caused by an allele that impairs production of dystrophin, a component of the sarcolemmal cytoskeleton. About one third of such cases are new mutations. What is the LEAST likely cause of the woman's muscle weakness?

1. Activation of Xist gene.
2. Turner syndrome.
3. Somatic mutation.
4. Unfortunate lyonization.

Analyze Systems:

You are involved in a marine habitat conservation project and find that that crab (Carcinus maenas) predation by herring gulls in the intertidal zone is 20x greater on sites lacking concealment cover of fronds of the rockweed Ascophyllum nodosum. How might you best characterize the ecological status of Ascophyllum in this situation?

1. Keystone species.
2. Umbrella species.
3. Flagship species.
4. Endangered species.
5. Foundation species.

Recognize Patterns:

A habitat conservancy group became alarmed when they performed a survey within a group of islands, and found only four species of fern on a small island whereas there were typically 16 species of fern on a larger islands. If this were a natural pattern of distribution, how might it best be explained?

1. Raunkiniaer’s rule.
2. Allen's rule.
3. Bergmann’s rule.
4. Shelford’s law.
5. Arrhenius equation.

Infer Causes:

A dog-owner noticed that her pet had an enlarged liver and shrunken muscles. If this were an osmotic problem, which explanation would be most appropriate?

1. Hypokalemia.
2. Hypernatremia.
3. Hyerkalemia.
4. Hyperglycemia.
5. Hypoglycemia.

Predict Effects:

Domoic acid, isolated from a diatom, has been found experimentally to bind to hippocampal glutamate receptors. If a person were to accidently consume shellfish contaminated with this organism, what effect might be expected?

1. Blindness.
2. Deafness.
3. Amnesia.
4. Aphasia.
5. Rigidity.

Calculate Values:

You are working for a biotech company that is attempting to develop a blood screening test for ovarian cancer. A preliminary assessment on a population in which the confirmed ovarian cancer rate is five per thousand shows that the test correctly diagnosed four out of every five cases of ovarian cancer but showed a false positive in 36 cases per thousand. If a woman tests positive, what is the probability that she has ovarian cancer?

1. 0.8
2. 0.6
3. 0.4
4. 0.2
5. 0.1

Calculate Outcomes:

Lannie and Phil both have healthy parents but each has a sister with autosomal recessive cystic fibrosis. If Lannie and Phil have a child, what is the probability that it will be born with cystic fibrosis?

1. 0
2. 1/2
3. 1/3
4. 1/9
5. 1/36

Critique Investigations:

A biologist studied the environmental impact of an herbicide on squirrel reproduction. He selected two small islands with similar vegetation and similar-sized squirrel populations (about 200 squirrels) with equal reproductive rates. One island, selected at random, was sprayed with herbicide, and the other was used as a control. Squirrel reproduction rates were measured on both islands before and after the treatment. What is the greatest flaw in this investigation?

1. Poor outcome measure.
2. Lack of controls.
3. Lack of replication.
4. Lack of randomization.

Weigh Arguments:

A man diagnosed with Parkinsonism suspected that pollution at his workplace (a mill) may be to blame. Which of the following statements would lend greatest support to his suspicion?

1. A survey of workers at the mill reveals many cases of illness.
2. A survey of workers at the mill and at other similar mills reveals many cases of illness.
3. The incidence of illness is higher among the mill workers than among age-matched workers in non-polluted workplaces.
4. The national average incidence of Parkinsonism is lower than that among workers at the mill.

Manipulate Data:

A coach is concerned about the electrolyte balance of an athlete performing in a warm climate. She estimates that ambient temperature and humidity conditions will result in a perspiration loss of about two liters of NaCl solution from the athlete during an Olympic event. The athlete weighs 50 kg and begins the event with a plasma sodium concentration of 140 mmol/L. Assume average sodium sweat-loss of 70 mmol/L, assume no water intake, and ignore kidney function. Approximately what would be the plasma sodium concentration at the end of the event?

1. 130 mmol/L
2. 135 mmol/L
3. 140 mmol/L
4. 145 mmol/L
5. 150 mmol/L

Critique Claims:

George claimed that a tropical animal protein supplied by a local naturopath was effective in lowering blood pressure, and George was planning to invest in the product. As evidence of his claim, George, who had hypertension, said that he felt much better after the treatment and had much more energy. In comparison to a credible scientific investigation, how is George's inference flawed?

1. Lack of an appropriate outcome measure.
2. Lack of appropriate controls and lack of an appropriate outcome measure.
3. Lack of randomization, lack of replication, and lack of an appropriate outcome measure.
4. Lack of replication and lack of appropriate controls.
5. Lack of appropriate outcome measure, replication, randomization, and controls.

Prioritize Questions:

Commercial fishers are concerned that sea lions are reducing the number of salmon available to the fishery. If the size of the salmon run were known, and if limited additional research funds were available and you were ranking proposals to investigate the salmon predation concern, which of the following investigations would you deem LEAST urgent?

1. Study of percentage of salmon in the sea lion diet.
2. Study of sea lion daily caloric requirement.
3. Study of sea lion population size.
4. Study of sea lion gut capacity.
5. Study of percentage of salmon-predators in the sea lion diet.

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Copyright 1999 Peter Ommundsen

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