Issues related to the validity and reliability of measurement instruments used in research are reviewed. Key indicators of the quality of a measuring instrument are the reliability and validity of the measures. The process of developing and validating an instrument is in large part focused on reducing error in the measurement process. Reliability estimates evaluate the stability of measures, internal consistency of measurement instruments, and interrater reliability of instrument scores. Validity is the extent to which the interpretations of the results of a test are warranted, which depends on the particular use the test is intended to serve. The responsiveness of the measure to change is of interest in many of the applications in health care where improvement in outcomes as a result of treatment is a primary goal of research. Several issues may affect the accuracy of data collected, such as those related to self-report and secondary data sources. Self-report of patients or subjects is required for many of the measurements conducted in health care, but self-reports of behavior are particularly subject to problems with social desirability biases. Data that were originally gathered for a different purpose are often used to answer a research question, which can affect the applicability to the study at hand. In health care and social science research, many of the variables of interest and outcomes that are important are abstract concepts known as theoretical constructs. Using tests or instruments that are valid and reliable to measure such constructs is a crucial component of research quality.

personality questionnaires designed to measure corresponding trait constructs in younger age ranges, such as the High School Personality Questionnaire (HSPQ) The Sixteen Personality Factor Questionnaire (16PF) is a self-reported personality test developed over several decades of empirical research by Raymond B. Cattell, Maurice Tatsuoka and Herbert Eber. The 16PF provides a measure of personality and can also be used by psychologists, and other mental health professionals, as a clinical instrument to help diagnose psychiatric disorders, and help with p The Sixteen Personality Factor Questionnaire (16PF) is a self-reported personality test developed over several decades of empirical research by Raymond B. Cattell, Maurice Tatsuoka and Herbert Eber. The 16PF provides a measure of personality and can also be used by psychologists, and other mental health professionals, as a clinical instrument to help diagnose psychiatric disorders, and help with prognosis and therapy planning. The 16PF can also provide information relevant to the clinical and counseling process, such as an individual's capacity for insight, self-esteem, cognitive style, internalization of standards, openness to change, capacity for empathy, level of interpersonal trust, quality of attachments, interpersonal needs, attitude toward authority, reaction toward dynamics of power, frustration tolerance, and coping style. Thus, the 16PF instrument provides clinicians with a normal-range measurement of anxiety, adjustment, emotional stability and behavioral problems. Clinicians can use 16PF results to identify effective strategies for establishing a working alliance, to develop a therapeutic plan, and to select effective therapeutic interventions or modes of treatment. It can also be used within other contexts such as career assessment and occupational selection. Beginning in the 1940s, Cattell used several techniques including the new statistical technique of common factor analysis applied to the English-l The Sixteen Personality Factor Questionnaire (16PF) is a self-reported personality test developed over several decades of empirical research by Raymond B. Cattell, Maurice Tatsuoka and Herbert Eber. The 16PF provides a measure of personality and can also be used by psychologists, and other mental health professionals, as a clinical instrument to help diagnose psychiatric disorders, and help with prognosis and therapy planning. Cattell and his co-workers also constructed downward extensions of the 16PF – parallel personality questionnaires designed to measure corresponding trait constructs in younger age ranges, such as the High School Personality Questionnaire (HSPQ) – now the Adolescent Personality Questionnaire (APQ) for ages 12 to 18 years, the Children's Personality Questionnaire (CPQ), the Early School Personality Questionnaire (ESPQ), as well as the Preschool Personality Questionnaire (PSPQ). & Schuerger, J.M, 2003) The 16PF traits are also included in the Psychological Evaluation Questionnaire (PEQ), which combines measures of both normal and abnormal personality traits into one test (Cattell, Cattell, Cattell, Russell, & Bedwell, 2003) == Raymond Cattell's 16 Personality Factors == Below is a table outlining the personality traits measured by the 16PF Questionnaire. == Relationship to five-factor models == In the Fourth and Fifth Editions of the 16PF, there were five global factors that seem to correspond fairly closely to the "Big Five personality traits". One major technique of factor analysis, the principal-components method, finds the minimum number of common factors that can account for an interrelated set of scores. Cattell's goal was to empirically determine and measure the essence of personality. Cattell used factor analysis to reduce thousands of psychological traits into what he believed to be 16 of the basic dimensions, or source traits of human personality. As a result, he created the 16PF personality test. == 16PF global and primary factors == == History and development == === Cattell physical sciences background === The 16PF Questionnaire was created from a fairly unusual perspective among personality tests. From this background in the physical sciences, Cattell developed the belief that all fields are best understood by first seeking to find the fundamental underlying elements in that domain, and then developing a valid way to measure and research these elements (Cattell, 1965). Personality research author Schuerger stated that: Cattell's goal in creating the 16PF Questionnaire was to provide a thorough, research-based map of normal personality. They wanted to include every known personality dimension in their investigation, and thus began with the largest existing compilation of personality traits (Allport and Odbert, 1936). Over time, they used factor Research has also supported the comprehensiveness of the 16PF traits: all dimensions on other major personality tests (e.g., the NEO Personality Inventory, the California Psychological Inventory, the Personality Research Form, and the Myers-Briggs Type Indicator) have been found to be contained within the 16PF scales in regression and factor-analytic studies (Conn & Rieke, 1994; Cattell, 1996). Since its release in 1949, the 16PF Questionnaire has been revised four times: once in 1956, once in 1962, once in 1968, and the current version was developed in 1993. The US version of the test was also re-standardized in 2002, along with the development of forms for children and teenagers; versions for the UK, Ireland, France and the Netherlands were re-standardised in 2011. Additionally, there is a shortened form available primarily for employee selection and the questionnaire has been adapted into more than 35 languages. The questionnaire has also been validated in a range of international cultures over time. The 16PF was distributed through the Institute for Personality and Ability Testing (IPAT), founded by Cattell and based in Savoy, Illinois.