Description Usage Arguments Value
Evaluates the standard deviation, correlation, difficulty, discrimination, and reliability of a set of test scores.
1 | item_analysis(data_mat)
|
data_mat |
A numeric matrix of test scores with rows representing each examinee and columns representing each question. Elements should equal to 1 (correct) or 0 (incorrect). |
Returns a list of the following statistics.
question |
Question names. |
sd |
Standard deviation of each question. |
correlation |
Pearson correlation coefficeint of each question with the average test score for each examinee. (Analogous to the point biserial correlation coefficient.) |
difficulty |
Average response for each question. High values indicate low difficulty. |
discrimination |
The ability of a question to differentiate between a high scoring student and a low scoring student. The statistic is bound between -1 and 1. The statistic for each question is caluclated using the top third scorers and the bottom third scorers. Questions with a large positive discrimination score indicates that examinees who performed well on this question also had high final test scores, and examinees who performed poorly on this question had low final test scores. |
reliability |
Calculated using the Kuder-Richardson Formula 20 (KR-20). Typically test reliability scores above 0.70 for classroom exams are preferred. (This is an overall statistic - not item-specific.) |
Add the following code to your website.
For more information on customizing the embed code, read Embedding Snippets.