A. 0.30 – 1
B. 1
C. 0.30
D. None
Answer is = A
You are correct! The discrimination power of an item is generally considered acceptable when its value ranges from:
A. 0.30 – 1
Here’s why this range is preferred:
- 0.30 represents a minimum threshold: A value below 0.3 indicates the item has weak discrimination power. It might not be effective in differentiating between high and low achievers on the test.
- 1 represents perfect discrimination: A value of 1 indicates the item perfectly separates high achievers (who answer correctly) from low achievers (who answer incorrectly). This is a rare case in practice.
An item with discrimination power between 0.30 and 1 suggests it can effectively distinguish between students with different levels of knowledge or skill related to the content being assessed. This is a crucial characteristic for ensuring the validity of a test.
It’s important to note that some sources might have slightly different ranges for acceptable discrimination power, depending on the specific testing context and desired level of stringency. However, the range of 0.30 to 1 is a widely used guideline.
Here are some additional points to consider:
- Visual inspection: Scatter plots or discrimination indices can be used to visually analyze how well an item separates high and low scorers.
- Statistical significance: Statistical tests can be used to assess whether the observed discrimination power is statistically significant.
In conclusion, a discrimination power between 0.30 and 1 is a good rule of thumb for acceptable test items. This range indicates the item can effectively discriminate between high and low achievers, promoting a valid assessment of the targeted knowledge or skills.