Fig. 2From: Revalidating a measurement instrument of spatial thinking ability for junior and high school students Item Characteristics Curves for the Item 1 (STAT1G) and Item 8 (STAT8G). Item 1 has a good agreement between the expected probability (the solid curve) and the observed probabilities (the dots). Item 8 has a poor agreement between the expected probability (the solid curve) and the observed probabilities (the dots)Back to article page