Jove
Visualize
Contact Us
JoVE
x logofacebook logolinkedin logoyoutube logo
ABOUT JoVE
OverviewLeadershipBlogJoVE Help Center
AUTHORS
Publishing ProcessEditorial BoardScope & PoliciesPeer ReviewFAQSubmit
LIBRARIANS
TestimonialsSubscriptionsAccessResourcesLibrary Advisory BoardFAQ
RESEARCH
JoVE JournalMethods CollectionsJoVE Encyclopedia of ExperimentsArchive
EDUCATION
JoVE CoreJoVE BusinessJoVE Science EducationJoVE Lab ManualFaculty Resource CenterFaculty Site
Terms & Conditions of Use
Privacy Policy
Policies

Related Concept Videos

Distributions to Estimate Population Parameter01:26

Distributions to Estimate Population Parameter

5.2K
The accurate values of population parameters such as population proportion, population mean, and population standard deviation (or variance) are usually unknown. These are fixed values that can only be estimated from the data collected from the samples. The estimates of each of these parameters are sample proportion, the sample mean, and sample standard deviation (or variance). To obtain the values of these sample statistics, data are required that have particular distribution and central...
5.2K
Confounding in Epidemiological Studies01:27

Confounding in Epidemiological Studies

853
Confounding in statistical epidemiology represents a pivotal challenge, referring to the distortion in the perceived relationship between an exposure and an outcome due to the presence of a third variable, known as a confounder. This variable is associated with both the exposure and the outcome but is not a direct link in their causal chain. Its presence can lead to erroneous interpretations of the exposure's effect, either exaggerating or underestimating the true association. This...
853
Pharmaceutical Equivalents01:26

Pharmaceutical Equivalents

205
As defined by regulatory standards, pharmaceutical equivalents require generic drug products to have identical dosage forms and chemically identical active pharmaceutical ingredients (APIs). They must adhere to compendial or applicable standards for potency, content uniformity, disintegration times, and dissolution rates. In the case of modified-release dosage forms, variations in drug content are permissible as long as the delivered amount remains consistent with the innovator drug product.
205
Equivalent Capacitance01:19

Equivalent Capacitance

2.2K
Multiple capacitors can be connected in a circuit in series or parallel configuration. When the capacitor combination is connected to a battery, the potential drop across each capacitor and the magnitude of charge stored in the individual capacitor depends on the type of the connection. The capacitor combination is replaced by a single equivalent capacitor that stores the same amount of charge as the combination for a given potential difference.
The following strategies are adopted to calculate...
2.2K
Equivalent Capacitance01:19

Equivalent Capacitance

714
From the study of resistive circuits, it is understood that employing a series-parallel combination serves as an effective strategy for simplifying circuits. Capacitors can be arranged within a circuit in one of two ways: a series configuration or a parallel configuration. The way these capacitors are connected to a battery will influence both the potential drop across each individual capacitor and the size of the charge that each capacitor can store. This is determined by the specific type of...
714
Strategies for Assessing and Addressing Confounding01:25

Strategies for Assessing and Addressing Confounding

420
Confounding is a critical issue in epidemiological studies, often leading to misleading conclusions about associations between exposures and outcomes. It occurs when the relationship between the exposure and the outcome is mixed with the effects of other factors that influence the outcome. Given that, addressing confounding is of high importance for drawing accurate inferences in research.
Confounding can be addressed at both the design phase of a study and through analytical methods after data...
420

You might also read

Related Articles

Articles linked to this work by shared authors, journal, and citation graph.

Sort by
Same author

"Distinct and Separate Issues": Examining US Adults' Attitudes Toward Abortion During COVID-19.

Perspectives on sexual and reproductive health·2025
Same author

A Study of Reverse-Worded Matched Item Pairs Using the Generalized Partial Credit and Nominal Response Models.

Educational and psychological measurement·2018
Same author

Effects of 28-Day Beta-Alanine Supplementation on Isokinetic Exercise Performance and Body Composition in Female Masters Athletes.

Journal of strength and conditioning research·2015
Same author

Differential Item Functioning in rehabilitation research.

Work (Reading, Mass.)·2010

Related Experiment Video

Updated: Feb 10, 2026

Three-Dimensional Echocardiographic Method for the Visualization and Assessment of Specific Parameters of the Pulmonary Veins
06:48

Three-Dimensional Echocardiographic Method for the Visualization and Assessment of Specific Parameters of the Pulmonary Veins

Published on: October 28, 2020

3.3K

Unidimensional IRT Item Parameter Estimates Across Equivalent Test Forms With Confounding Specifications Within

Ki Lynn Matlock1, Ronna Turner2

  • 1Oklahoma State University, Stillwater, OK, USA.

Educational and Psychological Measurement
|May 26, 2018
PubMed
Summary

Test developers should ensure consistent item difficulty and number within subcontent areas, not just overall, for accurate test form construction. This simulation study highlights potential biases in item parameter estimation.

Keywords:
Rasch modelitem difficultyitem discriminationitem response theory (IRT)multidimensional dataunidimensionality

More Related Videos

Patient-specific Modeling of the Heart: Estimation of Ventricular Fiber Orientations
12:09

Patient-specific Modeling of the Heart: Estimation of Ventricular Fiber Orientations

Published on: January 8, 2013

14.1K
Clinical Assessment of Spatiotemporal Gait Parameters in Patients and Older Adults
08:56

Clinical Assessment of Spatiotemporal Gait Parameters in Patients and Older Adults

Published on: November 7, 2014

14.3K

Related Experiment Videos

Last Updated: Feb 10, 2026

Three-Dimensional Echocardiographic Method for the Visualization and Assessment of Specific Parameters of the Pulmonary Veins
06:48

Three-Dimensional Echocardiographic Method for the Visualization and Assessment of Specific Parameters of the Pulmonary Veins

Published on: October 28, 2020

3.3K
Patient-specific Modeling of the Heart: Estimation of Ventricular Fiber Orientations
12:09

Patient-specific Modeling of the Heart: Estimation of Ventricular Fiber Orientations

Published on: January 8, 2013

14.1K
Clinical Assessment of Spatiotemporal Gait Parameters in Patients and Older Adults
08:56

Clinical Assessment of Spatiotemporal Gait Parameters in Patients and Older Adults

Published on: November 7, 2014

14.3K

Area of Science:

  • Psychometrics
  • Educational Measurement
  • Statistical Modeling

Background:

  • Test forms often aim for equivalent item counts and overall difficulty.
  • Variations in item difficulty and count within subcontent areas can occur.
  • Maintaining consistency across all test specifications is crucial for reliable assessments.

Purpose of the Study:

  • To investigate the impact of item difficulty and count variations within subcontent areas on test form equivalence.
  • To evaluate the accuracy of item parameter estimation under different simulation conditions.
  • To provide recommendations for test developers regarding test construction practices.

Main Methods:

  • A simulation study was conducted with six test forms.
  • Manipulated variables included item count and difficulty within subsets measuring specific dimensions.
  • Item parameters were estimated using Rasch and two-parameter logistic unidimensional item response theory models at varying correlation levels (0, .3, .6, .9).

Main Results:

  • Average unidimensional estimated discrimination remained consistent across forms with the same correlation.
  • Forms with more easy items in a subset were estimated as more difficult overall than those with harder items.
  • Bias measures were reported for item parameter estimates within subsets.

Conclusions:

  • Test developers must ensure consistent specifications not only for the entire test but also within subcontent areas.
  • Deviations in item difficulty and count within subsets can lead to biased parameter estimates.
  • Adhering to consistent specifications across all levels enhances the reliability and validity of multiple test forms.