Item Statistics Page Fields

Fields: Item Statistics Screen

Here is information about the fields (features) on the Item Statistics screen.

The unique identification number assigned to the item.

The response options associated with the item.

Domain associated to the item.

Sample Population: N-Size

Number of examinees in the calibration sample for the selected sample.

Sample Population: Mean Score

Average raw score for the selected sample.

Sample Population: SD Score

Standard deviation of raw scores for the item for the selected sample.

Sample Population: Minimum Score

Minimum raw score for the item for the selected sample.

Sample Population: Maximum Score

Maximum raw score for the item for the selected sample.

Sample Population: Alpha Reliability

Cronbach’s alpha reliability index for the selected sample.

Sample Population: Adj. Alpha Reliability

Adjusted alpha reliability index for the selected sample.

Sample Population: Item Total Correlation

Correlation between scores on the item and the total test.

Sample Population: Adj. Item Total Correlation

Correlation between scores on the item and the total test adjusted to remove the item from the total.

Sample Population: Percent Omit

Parameter for the selected sample.

Sample Population: % Options

Statistical measure for the displayed item. There are a variable number <n> of these values.

Selection or specification of the group.

Uniform parameter for the selected DIF group.

Probability parameter for the selected DIF group.

Non-Uniform parameter for the selected DIF group.

Non-Uniform Prob.

Probability parameter for the selected DIF group.

Calibration Sample: Description

Description of the sample used for calibration.

Calibration Sample: Sample Population

The sample based on which the item calibration was conducted.

Item Response Theory model used for calibration.

Category Response Function

Image of a graph for this item. Paperclip image is a button to attach a new image for the Category Response Function graph.

Item Information Function

Image of a graph for this item. Paperclip image is a button to attach a new image for the Item Information Function graph.

X2 item fit index based on sum score (“Value”).

G2 item fit index based on sum score (“Value”).

X2 item fit index based on Theta (“Prob”).

G2 item fit index based on Theta (“Prob”).

Loevinger H Scalability

The Loevinger H coefficient of scalability (monotonicity): weak (0.3 £ H < 0.4), medium (0.4 £ H < 0.5) and strong (H > 0.5)

Location at Max Information

Theta location where item information is at its maximum.

IRT Parameters: Slope

IRT discrimination parameter.

IRT Parameters: Guessing

The probability that very low ability individuals will get the item correct by chance (applicable to dichotomously scored cognitive items).

IRT Parameters: Thresholds

IRT threshold / category boundary parameters. There are a variable number of these values based on the number of categories for the item. The maximum number of instances equals (1 – (number of responses for the item)).

Presents a dialog box with editable fields.

Navigates back to the previous screen.

Presents a new instance of editable fields.

Saves changes and updates.

Does not save any changes.

Fields: Item Statistics Screen Here is information about the fields (features) on the Item Statistics screen.
ID	The unique identification number assigned to the item.
Responses	The response options associated with the item.
Domain	Domain associated to the item.
Sample Population: N-Size	Number of examinees in the calibration sample for the selected sample.
Sample Population: Mean Score	Average raw score for the selected sample.
Sample Population: SD Score	Standard deviation of raw scores for the item for the selected sample.
Sample Population: Minimum Score	Minimum raw score for the item for the selected sample.
Sample Population: Maximum Score	Maximum raw score for the item for the selected sample.
Sample Population: Alpha Reliability	Cronbach’s alpha reliability index for the selected sample.
Sample Population: Adj. Alpha Reliability	Adjusted alpha reliability index for the selected sample.
Sample Population: Item Total Correlation	Correlation between scores on the item and the total test.
Sample Population: Adj. Item Total Correlation	Correlation between scores on the item and the total test adjusted to remove the item from the total.
Sample Population: Percent Omit	Parameter for the selected sample.
Sample Population: % Options	Statistical measure for the displayed item. There are a variable number <n> of these values.
DIF groups	Selection or specification of the group.
Uniform	Uniform parameter for the selected DIF group.
Uniform Prob.	Probability parameter for the selected DIF group.
Non-Uniform	Non-Uniform parameter for the selected DIF group.
Non-Uniform Prob.	Probability parameter for the selected DIF group.
Calibration Sample: Description	Description of the sample used for calibration.
Calibration Sample: Sample Population	The sample based on which the item calibration was conducted.
IRT Model	Item Response Theory model used for calibration.
Category Response Function	Image of a graph for this item. Paperclip image is a button to attach a new image for the Category Response Function graph.
Item Information Function	Image of a graph for this item. Paperclip image is a button to attach a new image for the Item Information Function graph.
S-X²	X2 item fit index based on sum score (“Value”).
S-G²	G2 item fit index based on sum score (“Value”).
X²	X2 item fit index based on Theta (“Prob”).
G²	G2 item fit index based on Theta (“Prob”).
Loevinger H Scalability	The Loevinger H coefficient of scalability (monotonicity): weak (0.3 £ H < 0.4), medium (0.4 £ H < 0.5) and strong (H > 0.5)
Location at Max Information	Theta location where item information is at its maximum.
IRT Parameters: Slope	IRT discrimination parameter.
IRT Parameters: Guessing	The probability that very low ability individuals will get the item correct by chance (applicable to dichotomously scored cognitive items).
IRT Parameters: Thresholds	IRT threshold / category boundary parameters. There are a variable number of these values based on the number of categories for the item. The maximum number of instances equals (1 – (number of responses for the item)).
Update	Presents a dialog box with editable fields.
Back	Navigates back to the previous screen.
New	Presents a new instance of editable fields.
Save	Saves changes and updates.
Cancel	Does not save any changes.