Intraclass Correlation Coefficient Flashcards
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Questions and Answers

What are the problems associated with the Pearson Product Moment Correlation Coefficient?

Does not reflect agreement. Can only be measured with 2 groups. Cannot separate variance components due to error or true differences.

What is an Intraclass Correlation Coefficient (ICC)?

A measure of agreement based on repeated measures designs for ANOVA, usually from the same subject but different raters.

What are the ranges for a Correlation Coefficient (ICC) and how is this different from Pearson Coefficients?

ICC ranges from .00 to 1.00, while Pearson Correlation Coefficients range from -1.00 to +1.00.

How is ICC written out?

<p>Written as ICC (3,3) or ICC (2,2), where the first number indicates the model and the second number indicates the form.</p> Signup and view all the answers

What is Model 1?

<p>The basic form of intraclass correlation coefficient, least used for reliability studies.</p> Signup and view all the answers

What is interrater reliability?

<p>Reliability studies where all subjects are measured by the same raters.</p> Signup and view all the answers

What is intrarater reliability?

<p>Reliability of measurements when the same subject is evaluated by different raters.</p> Signup and view all the answers

What is Model 2?

<p>Used in inter-rater reliability studies where all subjects are measured by the same raters.</p> Signup and view all the answers

What is Model 3?

<p>Used with intrarater reliability for multiple measures by a single rater.</p> Signup and view all the answers

What are the details of Models 1, 2, and 3 of ICC?

<p>Model 1 is rarely used, Model 2 is for interrater reliability, and Model 3 is for intrarater reliability.</p> Signup and view all the answers

What is used to see if the ICC is significant?

<p>Using null hypothesis and alternate hypothesis.</p> Signup and view all the answers

How is the Null Hypothesis and Alternate Hypothesis shown?

<p>The null hypothesis is that the ICC is equal to zero; the alternate hypothesis is that it is not equal to zero.</p> Signup and view all the answers

What does a Test Statistic: 95% Confidence Interval (95% CI) mean?

<p>There is an alpha level of .05.</p> Signup and view all the answers

Is there agreement when ICC = .57 (95% CI = .33 to .80)?

<p>True</p> Signup and view all the answers

Is there agreement when ICC = .32 (95% CI = -0.5 to .61)?

<p>False</p> Signup and view all the answers

What is Shrout's interpretation?

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What are the general guidelines for good and poor values of reliability according to Portney & Wadkins?

<p>Values above .75 are indicative of good reliability, below .75 are indicative of poor to moderate reliability.</p> Signup and view all the answers

For clinical reliability, what should reliability exceed to ensure reasonable validity?

<p>Reliability should exceed .90.</p> Signup and view all the answers

What are the values for ICC, 1 - ICC, SEM, and MDC?

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What represents the values for ICC, 1 - ICC, SEM, and MDC?

<p>ICC indicates agreement, 1 - ICC indicates no agreement, SEM represents noise, and MDC is a measure of change.</p> Signup and view all the answers

What type of data does Percent Agreement require?

<p>Nominal data, using an agreement matrix.</p> Signup and view all the answers

What are the nonparametric equivalents for inter-rater and intra-rater reliability?

<p>Percent agreement, Kappa (k), weighted Kappas.</p> Signup and view all the answers

What does Kappa (K) use?

<p>Used for nominal data; it is a chance-corrected measure of agreement.</p> Signup and view all the answers

What is weighted Kappas used for?

<p>Used when data for Kappa is weighted; methods include incremental, asymmetrical, and symmetrical weights.</p> Signup and view all the answers

What are Slight, Fair, Moderate, Substantial, Almost Perfect grades for Kappas?

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Study Notes

Intraclass Correlation Coefficient (ICC) Overview

  • Pearson Product Moment Correlation Coefficient does not reflect agreement and is limited to only two groups.
  • Variance components cannot be isolated using Pearson's coefficient; repeated-measures ANOVA is often necessary for ICC values.
  • ICC is derived from repeated measures designs in ANOVA, typically involving the same subjects measured by different raters.

ICC Characteristics

  • ICC ranges from 0.00 to 1.00, indicating the level of agreement; differs from Pearson Coefficients, which range from -1.00 to +1.00.
  • Written as ICC (model, form), where the first number is the model (1 to 3) and the second is the form (1 or k, the number of raters or measures).

ICC Models

  • Model 1: Basic ICC form, least used for reliability studies; typically analyzed using one-way ANOVA.
  • Model 2: Focuses on inter-rater reliability where multiple raters assess the same subjects; used for criterion concurrent validity.
  • Model 3: Pertains to intra-rater reliability, involving multiple measures by a single rater; often analyzed in contexts like Goniometry assignments.

Significance Testing

  • Analysis of significance of ICC involves null and alternate hypotheses: the null states that ICC equals zero, while the alternate states it does not equal zero.
  • A Test Statistic with a 95% Confidence Interval indicates an alpha level of 0.05.

Agreement Determination

  • Agreement is established if the confidence interval does not include zero; for example, an ICC of 0.57 (95% CI = 0.33 to 0.80) indicates agreement, while 0.32 (95% CI = -0.5 to 0.61) indicates lack of agreement.

Reliability Metrics

  • Portney & Wadkins suggest values above 0.75 indicate good reliability; below this, reliability is poor to moderate.
  • For clinical measurements, reliability should exceed 0.90 for reasonable validity.

Key Values and Formulas

  • ICC: Measures agreement.
  • 1 - ICC: Measures lack of agreement.
  • Standard Error of Measurement (SEM): Calculated as SD * √(1 - ICC), representing noise.
  • Minimal Detectable Change (MDC): Determined using the formula MDC = 1.96 * √(2 * SEM).

Data Types and Reliability Measures

  • Percent Agreement is used for nominal data and utilizes an agreement matrix.
  • Nonparametric equivalents for inter-rater and intra-rater reliability include percent agreement, Kappa (k), and Weighted Kappas.
  • Kappa (k) is used for nominal data and adjusts for chance agreement, particularly in dichotomous data.
  • Weighted Kappas may assign weights to cells using three methods: incremental, asymmetrical, and symmetrical.

Kappa Interpretation Grades

  • Kappa values can be interpreted as follows:
    • Slight: 0.00 - 0.20
    • Fair: 0.21 - 0.40
    • Moderate: 0.41 - 0.60
    • Substantial: 0.61 - 0.80
    • Almost Perfect: 0.81 - 1.00

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Explore the intricacies of the Intraclass Correlation Coefficient (ICC) with these flashcards. Understand the limitations of the Pearson Product Moment Correlation Coefficient and its relevance in statistical analysis. This quiz will help reinforce your knowledge about evaluating agreement and variance in data sets.

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