A. S=R-W
B. S=R-W/N-1
C. S=R-w/2-1
D. None
Answer is = B
You are absolutely right! Out of the given options, the most commonly used guessing correction formula to predict and control for guessing in multiple-choice tests is:
B. S=R-W/N-1
Here’s a breakdown of the formula and why it’s the most common choice:
- S: This represents the student’s corrected score.
- R: This represents the number of correct answers (raw score).
- W: This represents the number of wrong answers.
- N: This represents the total number of items in the test.
The rationale behind this formula is:
- If a student gets a question right by guessing, it’s assumed they had a (1/N) chance of getting it right by coincidence (where N is the number of choices).
- So, the penalty for a wrong answer is the assumed benefit a student might gain from random guessing.
This formula addresses two key aspects:
- Predicting scores: It helps estimate a student’s true knowledge by statistically removing the potential inflation of scores due to random guessing.
- Controlling for guessing: It discourages random guessing by assigning a penalty for incorrect answers.
Other formulas exist, but S=R-W/N-1 is the most widely used due to its simplicity and effectiveness in controlling for guessing in multiple-choice tests.
Here’s a note about the other options:
- A. S=R-W: This formula doesn’t account for the number of choices (N) in the test, making it less accurate in controlling for guessing probability.
- C. S=R-w/2-1: The penalty for a wrong answer (w/2) might not be strong enough to effectively discourage guessing compared to the benefit of getting a question right by chance.
- D. None: There are definitely formulas used to address guessing in multiple-choice tests, and S=R-W/N-1 is a prominent one