Source Credibility Measures

Abstract

The Source Credibility Measures instrument, developed by James C. McCroskey and J. J. Teven in 1999, represents a refinement of earlier ethos and credibility scales utilized primarily within the field of communication studies. This 18-item scale is designed to measure an individual’s perception of a source (such as a manager or supervisor) based on three distinct, underlying factors: Competence, Trustworthiness, and Caring/Goodwill. It utilizes a semantic differential format to assess audience reactions, providing a robust measure for understanding the persuasive impact and relationship dynamics associated with the source.

Keywords

Source Credibility, Ethos, Competence, Trustworthiness, Goodwill, Caring, Persuasion, Communication, Organizational Communication, Measurement Scale

Authors

James C. McCroskey, J. J. Teven

Purpose

The primary purpose of the Source Credibility Measures scale is to provide researchers and practitioners with a highly reliable and valid instrument for assessing the perceived credibility of a source, particularly in organizational or interpersonal contexts (e.g., supervisor-subordinate relationships). While McCroskey had established foundational credibility scales in the 1960s and 1970s, the 1999 revision, published with Teven, focused specifically on re-examining and isolating the Goodwill (or Caring) dimension. This refinement was crucial because earlier models often confounded Goodwill with Trustworthiness, leading to less precise measurement. The scale allows for the quantitative assessment of how an audience perceives a source’s expertise, character, and intent toward them.

Construct

The scale measures the overarching construct of Source Credibility, which is defined as the attitude toward a source of communication held at a given time by a receiver. This attitude is multidimensional, broken down into three primary psychological factors:

• Competence: The degree to which the source is perceived as knowledgeable, intelligent, expert, trained, and informed on the subject matter or task. It assesses the source’s perceived ability.
• Trustworthiness: The dimension of character, including honesty, honor, morality, and ethics. A trustworthy source is perceived as reliable and sincere.
• Caring/Goodwill: The perception that the source has the receiver’s best interests at heart, is sensitive, concerned, and not self-centered. This factor is crucial in establishing positive relational dynamics.

The scale utilizes bipolar adjectives anchored on a 7-point continuum to capture the nuanced perception of these three factors.

Validity

The validity of this instrument has been extensively studied, building upon decades of research into ethos and credibility measurement pioneered by McCroskey. The 1999 revision specifically addressed the construct validity of the Goodwill dimension, demonstrating that it functions as a distinct factor separate from Trustworthiness. Construct validity is supported through factor analytic methods (detailed below), showing that the items designed to measure each factor load appropriately onto their designated dimensions. Furthermore, the scale exhibits predictive validity, correlating significantly with key communication outcomes, such as attitude change and audience compliance.

Reliability

High internal consistency is a hallmark of the Source Credibility Measures. The 1999 study confirmed strong reliability across all three factors, typically reporting Cronbach’s alpha coefficients well above the acceptable standard of 0.70 for all subscales (Competence, Trustworthiness, and Goodwill). The scale’s reliability ensures that the items consistently measure the intended construct across different applications and populations.

Factor Analysis

The Source Credibility Measures utilize a three-factor structure, which was confirmed through exploratory and confirmatory factor analysis in the foundational research. This analysis confirmed the existence of three orthogonal (independent) dimensions underlying the 18 items:

1. Competence Factor (Items 1, 2, 7, 11, 13, and 16).
2. Caring/Goodwill Factor (Items 3, 5, 8, 9, 15, and 18).
3. Trustworthiness Factor (Items 4, 6, 10, 12, 14, and 17).

This factor structure is consistent with the theoretical framework suggesting that a source must be perceived as both expert and trustworthy, and, crucially, must be perceived as caring about the receiver (Goodwill) for maximum persuasive effectiveness.

Instrument

Test Type: Psychometric Scale (Attitudinal)

Format: 18 items utilizing a 7-point Semantic Differential Scale format, with bipolar adjectives (e.g., Intelligent/Unintelligent). Certain items are reverse-coded for calculation.

Language Available: English (Original)

Population Group: General population, often used in organizational settings (assessing managers, supervisors, instructors) or political communication contexts.

Age Group: Adults (typically 18+)

Population Details: Applicable wherever a source-receiver relationship exists and credibility is a relevant variable.

Test Methodology: Respondents indicate their perception of the source by selecting a number (1 through 7) between opposing adjective pairs. Scores are summed within each factor after reverse-coding specified items (*). Higher scores indicate higher perceived credibility on that specific factor.

Keywords

McCroskey, Teven, Communication Monographs, Supervisor Assessment, Organizational Behavior, Ethos Measurement, Semantic Differential

Authors

Author ORCID Identifier: N/A (Information not provided in source material)

Affiliation Email addresses: N/A (Information not provided in source material)

Correspondence Address: N/A (Information not provided in source material)

Permissions & Fee and Test Year

The scale was published in its refined form in 1999. The instrument is often made available for academic research purposes by the authors without a fee. The original PDF describing the instrument and its use can be downloaded here: http://www.jamescmccroskey.com/publications/180.pdf. Additional information is available on the author’s website: http://www.jamescmccroskey.com/measures/source_credibility.htm.

Reference’s

The development and theoretical background of the scale draw upon multiple foundational works, including:

• McCroskey, J. C., & Mehrley, R. S. (1969). The effects of disorganization and nonfluency on attitude change and source credibility. Speech Monographs, 36, 13-21.
• McCroskey, James C. (1966) “Scales for the Measurement of Ethos”, Speech Monographs, 33(1), p.65-72.
• McCroskey, James C.; Holdrige, William; Toomb, J. Kevin (1974) “An Instrument for Measuring the Source Credibility of Basic Speech Communication Instructors”, Speech Teacher, 2, p.26-33.
• McCroskey, James C.; Young, Thomas J. (1981) “Ethos and Credibility: The Construct and Its Measurement After Three Decades”, Central States Speech Journal, 32(1), p.24-34.
• McCroskey, J. C., &Teven, J. J. (1999). Goodwill: A reexamination of the construct and its measurement. Communication Monographs, 66, 90-103.

Items of the Source Credibility Measures

IMPORTANT: The following scale items must be preserved in their original language and must not be changed in any way.