irt (ck-sk)......؟
إجابة الطالب المختصرة من خلال موقع بوابة الإجابات هي
ck
It seems like you're asking about Item Response Theory (IRT) and specifically mentioning "ck" and "sk." These are likely referring to item parameters within an IRT model. To give you a comprehensive answer, let's break down IRT and these parameters:
**Item Response Theory (IRT): A Quick Overview**
IRT is a statistical framework for analyzing responses to tests, questionnaires, and other assessments. Unlike classical test theory (CTT), which focuses on the overall test score, IRT models focus on the **individual items** and how well they discriminate between individuals with different levels of the underlying trait being measured.
**Key Concepts in IRT**
* **Latent Trait (θ - theta):** This is the unobservable construct or ability being measured (e.g., math ability, depression level, extraversion). Individuals are assumed to have different levels of this trait.
* **Item Response Function (IRF):** This is the heart of IRT. It's a mathematical function that relates a person's latent trait level (θ) to the probability of them answering a particular item correctly (in a cognitive test) or endorsing a particular item (in a personality or attitude scale).
* **Item Parameters:** These are the characteristics of the individual items that describe how well the item functions in measuring the latent trait. This is where "ck" and "sk" likely come in.
**Common IRT Models and Item Parameters**
Several different IRT models exist, each with its own assumptions and item parameters. The most common models include:
1. **1-Parameter Logistic (1PL) Model (Rasch Model):**
* *Parameter:* **b (item difficulty)** - This represents the trait level at which a person has a 50% chance of answering the item correctly. Higher 'b' means the item is more difficult.
* *Limitations:* Assumes all items have equal discrimination.
2. **2-Parameter Logistic (2PL) Model:**
* *Parameters:*
* **a (item discrimination)** - This represents how well the item differentiates between people with different levels of the trait. A higher 'a' means the item is better at discriminating.
* **b (item difficulty)** - Same as in the 1PL model.
* *Advantages:* Allows items to have different levels of discrimination.
3. **3-Parameter Logistic (3PL) Model:**
* *Parameters:*
* **a (item discrimination)** - Same as in the 2PL model.
* **b (item difficulty)** - Same as in the 2PL model.
* **c (pseudo-guessing parameter)** - This represents the probability that a person with very low ability will answer the item correctly just by guessing. This is relevant for multiple-choice tests where guessing is possible.
4. **Graded Response Model (GRM):** This model is used for items with ordered response categories (e.g., Likert scales: Strongly Disagree, Disagree, Neutral, Agree, Strongly Agree).
* *Parameters:*
* **a (item discrimination)** - Same as in the 2PL and 3PL models.
* **b
i (category threshold parameters)** - These parameters represent the trait level at which a person has a 50% probability of endorsing a response category or higher. There is a separate 'b' parameter for each category boundary.
5. **Generalized Partial Credit Model (GPCM):** Similar to the GRM, but more flexible. Used for items with ordered response categories, but doesn't require the distances between categories to be equal.
* *Parameters:*
* **a (item discrimination)** - Same as in the 2PL and 3PL models.
* **b
i (step difficulty parameters)** - These parameters represent the difficulty of transitioning from one response category to the next.
**Likely Meanings of "ck" and "sk"**
Given the context of IRT, "ck" and "sk" are likely referring to:
* **ck:** Most probably refers to *category* parameter k for category k of items, as found in the GPCM model, to model items that are polytomous.
* **sk:** This can also mean the *step* parameters as found in the GPCM model, to model the probability of correctly answering the question.
**How to determine correct meaning:**
* **Consider the item:** How many possible answers/scores are there? 2? More than 2?
* **What software is being used:** What IRT Software (e.g., IRTPRO, mirt, ltm) and Model (e.g., 2PL, GPCM) are you using? Different software and models use different notations.
**In summary:**
IRT is a powerful tool for analyzing test data and understanding how individual items function. The specific item parameters (like the ones you mentioned) depend on the IRT model being used. If you can clarify which IRT model you're working with, I can provide a more precise explanation of what "ck" and "sk" represent in that specific context.
اذا كان لديك إجابة افضل او هناك خطأ في الإجابة علي سؤال irt (ck-sk)...... اترك تعليق فورآ.
