The phrase "average item difficulty" is correct and usable in written English.
It can be used in contexts such as educational assessments, surveys, or any situation where the difficulty level of items (like questions or tasks) is being evaluated or discussed.
Example: "The average item difficulty of the test was calculated to ensure that it was appropriate for the students' skill levels."
Alternatives: "mean item difficulty" or "typical item difficulty".
Furthermore, light propagation is an easier content topic (average item difficulty = −0.53) than visibility (average item difficulty = −0.10).
Additionally, the overall difficulties reveal that tier 1 is quite easy (average item difficulty = −0.61) compared to tier 2 (average item difficulty = −0.02).
The average item difficulty was 0.27 logits (SD = 0.96); the average person ability was −0.27 logits.
As the table shows, there is no clear pattern in difficulty of the items according to tier, because both tiers have average item difficulty estimates that are negative.
Average item difficulty was approximately one standard deviation below the ability scale mean, supporting the task's sensitivity to individual differences within the ability range of patients with WM impairment, but not within the range of most controls.
The average item difficulty was −0.62 logits for Level 1, 0.45 logits for Level 2, and 1.25 logits for Level 3. The discriminatory power of the different levels in the model is also shown in Figure 2 from the fact that none of the items from Levels 2 and 3 had a difficulty below the arithmetic mean of Level 1.
The preliminary explanatory IRT analysis carried out in (Hole et al. 2015) showed that for the Norwegian TIMSS 2011 grade 8 mathematics data, the dependence on formulas (corresponding to the category F) led to a relatively large average increase in item difficulty.
Tables 1 and 2 represent item difficulty, average measures, step calibrations, and item and category fit indices for self- and proxy-reports.
Values of item difficulty were on average 37 (Range: 6 – 58), indicating moderate to difficult item difficulties.
Furthermore, the PREE was shown to be well-targeted with a person-item location slightly less than the average of zero logits, which discounts item difficulty as a problem (See Fig. 2).
The multilevel testlet model perform the best when the item difficulty is low and medium with small average bias (−0.02 and −0.04), and perform the worst when the item difficulty is high with large average bias (0.92), which can be explained by the sparse cells due to high difficulty, resulting in extreme solutions.
