Test and measurements chapter 6

Item Response Theory

This examines how well individual items discriminates between; showcasing who does and does not know the material

• Emphasis on “Items”

Underlying ability is also know as a

Latent Trait

What represents the X-Axis of the Item Characteristic Curve

The amount of Latent trait or ability

What represents the Y-Axis of the Item Characteristic Curve

Probability of getting a question right 

What does theta represent?

Another representation of ability

If the average(mean) ability on an ICC is 0, what happens if you fall to the left or right of the mean

Left of the mean means below average, while right to the mean is above average

Difficulty level for the ICC

This is indicated by location on the X-axis

• The farther the right, the more difficult the item

The discrimination level for the ICC

This is indicated by the steepness of the curve 

• Steeper curve = Better item discrimination 

The Item Characteristic Curve helps us do what?

Looks at the relationship between performance on each individual item, and the underlying ability (Latent Trait) of each test taker