In a quest to make the best exams possible, I will discuss different types of questions and how to improve them. Today’s topic is the inaccurate question.
They happen to the best of us. We write a question, and it seems straightforward. It isn’t until later (sometimes much later) that we learn that the question is actually inaccurate. It includes wrong information or is multiple choice but does not show the right answer. It confuses the students who know the material, and can even lead students to answer other questions incorrectly.
If you notice a question is inaccurate, the first thing to do is remove it. If students have already taken the test, give them credit for a correct answer without regard to which answer they gave.
You may not even realize that you have a bad question until a student confronts you about it. One reason we leave inaccurate questions in a test is because the nature of how we teach introductory subjects.
When one is learning a subject for the first time, we tend to tell the students flat obvious rules about how things work, even when we know that there are exceptions. We use words like “all” and “never” that are absolute. We also generalize, knowing that the student hasn’t been taught about any of the exceptions yet. This tends to penalize students who read ahead, or who have outside knowledge about the subject.
What is the pH of the small intestine?
I found this question in an old test. There was probably a reason for this question. Perhaps it was meant to show that chemicals were released into the small intestine that counteract the acidity of the stomach. Perhaps it was meant in comparison to the stomach, I don’t know. But the question is inaccurate because none of the answers is strictly true.
Why it’s wrong
The pH is a number that tells how many hydrogen ions are in a solution. Numbers below 7 are acidic, above 7 are basic. Distilled water has a pH of 7 and is called neutral. In his article “Intraluminal pH of the human gastrointestinal tract”, J. Fallingborg writes that the pH changes along the length of the small intestine. After coming from the stomach, the pH is rapidly increased from very acidic (pH 2) to about pH 6 which is slightly acidic. As it travels through the small intestine, the pH rises to about 7.4 which is slightly basic before dropping down to 5.7 as it enters the large intestine.
The question is inaccurate because the pH of the small intestine could be said to be acidic, basic, and neutral. “About neutral” would be the most accurate answer to the question as the pH stays within two points of 7, and yet, for the majority of the time it is acidic. The question for the student becomes, ‘which answer does my instructor want me to give?’, not ‘which answer is correct’, since they all are.
How to improve the question?
1.Be more specific
Ask the pH of the duodenum or the illium or the caecum. And give specific pH number’s like 6 or 5.7, that might spur memories of a particular passage in the notes. One could also ask about the mechanism. What enzyme spurs the production of sodium bicarbonate raising the pH of the lumen? (Secretin). Or How does the pH change after entering the small intestine from the stomach? (It increases).
2. Change the type of question.
If the question were an essay question, this would not be as much of a problem. It would still be a bit too unspecific. Will every pH that is possible to find in the small intestine be counted as a correct answer? What if the person had inflammatory bowel disease that could cause fluctuations in intestinal pH? A better question would be…
Describe the pH of the intestine, and explain what factors affect it.
This allows the student to discuss what they know about intestinal pH and encourages them to add more information if possible. It encourages them to go deeper. Many teachers will call such a question harder than the first one because it requires more effort to answer, but if your student knows the answer, the first question is harder because it does not allow for an answer that is completely correct and therefore requires guessing what the teacher wants.
Inaccurate questions penalize your best students. Students who guess the answer do just as well or better than the students who know the answer. Inaccurate questions derail your good students and make the test seem more unfair and superficial.
Do you have a different opinion, or do you remember an inaccurate question that you observed on a test? Leave a comment below.