Written past times Colin Phelan in addition to Julie Wren, Graduate Assistants, UNI Office of Academic Assessment (2005-06).
Reliability is the bird to which an assessment tool produces stable in addition to consistent results.
Types of Reliability
1. Test-retest reliability is a mensurate of reliability obtained past times administering the same bear witness twice over a menstruation of fourth dimension to a grouping of individuals. The scores from Time 1 in addition to Time 2 tin thus live correlated inwards social club to evaluate the bear witness for stability over time.
Example: Influenza A virus subtype H5N1 bear witness designed to assess educatee learning inwards psychology could live given to a grouping of students twice, alongside the minute direction maybe coming a calendar week subsequently the first. The obtained correlation coefficient would betoken the stability of the scores.
2. Parallel forms reliability is a mensurate of reliability obtained past times administering dissimilar versions of an assessment tool (both versions must comprise items that probe the same construct, skill, cognition base, etc.) to the same grouping of individuals. The scores from the ii versions tin thus live correlated inwards social club to evaluate the consistency of results across alternate versions.
Example: If yous wanted to evaluate the reliability of a critical thinking assessment, yous mightiness exercise a large laid upward of items that all pertain to critical thinking in addition to thus randomly divide the questions upward into ii sets, which would correspond the parallel forms. Inter-rater reliability is a mensurate of reliability used to assess the bird to which dissimilar judges or raters concord inwards their assessment decisions.
3. Inter-rater reliability is useful because human observers volition non necessarily translate answers the same way; raters may disagree equally to how good surely responses or cloth demonstrate cognition of the build or science beingness assessed.
Example: Inter-rater reliability mightiness live employed when dissimilar judges are evaluating the bird to which fine art portfolios come across surely standards. Inter-rater reliability is peculiarly useful when judgments tin live considered relatively subjective. Thus, the utilization of this type of reliability would in all likelihood live to a greater extent than probable when evaluating artwork equally opposed to math problems.
4. Internal consistency reliability is a mensurate of reliability used to evaluate the bird to which dissimilar bear witness items that probe the same build make similar results.
a. Average inter-item correlation is a subtype of internal consistency reliability. It is obtained past times taking all of the items on a bear witness that probe the same build (e.g., reading comprehension), determining the correlation coefficient for each couplet of items, in addition to finally taking the average of all of these correlation coefficients. This lastly stride yields the average inter-item correlation.
b. Split-half reliability is about other subtype of internal consistency reliability. The procedure of obtaining split-half reliability is begun past times “splitting inwards half” all items of a bear witness that are intended to probe the same surface area of cognition (e.g., World War II) inwards social club to cast ii “sets” of items. The entire bear witness is administered to a grouping of individuals, the full grade for each “set” is computed, in addition to finally the split-half reliability is obtained past times determining the correlation betwixt the ii full “set” scores.
Validity refers to how good a bear witness measures what it is purported to measure.
Why is it necessary? While reliability is necessary, it lonely is non sufficient. For a bear witness to live reliable, it also needs to live valid. For example, if your scale is off past times v lbs, it reads your weight every twenty-four hr menstruation alongside an excess of 5lbs. The scale is reliable because it consistently reports the same weight every day, but it is non valid because it adds 5lbs to your truthful weight. It is non a valid mensurate of your weight.
Types of Validity
1. Face Validity ascertains that the mensurate appears to live assessing the intended build nether study. The stakeholders tin easily assess expression upward validity. Although this is non a real “scientific” type of validity, it may live an essential constituent inwards enlisting motivation of stakeholders. If the stakeholders exercise non believe the mensurate is an accurate assessment of the ability, they may travel disengaged alongside the task. Example: If a mensurate of fine art appreciation is created all of the items should live related to the dissimilar components in addition to types of art. If the questions are regarding historical fourth dimension periods, alongside no reference to whatever artistic movement, stakeholders may non live motivated to laissez passer on their best endeavor or invest inwards this mensurate because they exercise non believe it is a truthful assessment of fine art appreciation.
2. Construct Validity is used to ensure that the mensurate is genuinely mensurate what it is intended to mensurate (i.e. the construct), in addition to non other variables. Using a panel of “experts” familiar alongside the build is a means inwards which this type of validity tin live assessed. The experts tin examine the items in addition to determine what that specific particular is intended to measure. Students tin live involved inwards this procedure to obtain their feedback. Example: Influenza A virus subtype H5N1 women’s studies computer programme may blueprint a cumulative assessment of learning throughout the major. The questions are written alongside complicated wording in addition to phrasing. This tin effort the bear witness inadvertently becoming a bear witness of reading comprehension, rather than a bear witness of women’s studies. It is of import that the mensurate is genuinely assessing the intended construct, rather than an extraneous factor.
3. Criterion-Related Validity is used to predict time to come or electrical flow functioning – it correlates bear witness results alongside about other criterion of interest. Example: If a physics computer programme designed a mensurate to assess cumulative educatee learning throughout the major. The novel mensurate could live correlated alongside a standardized mensurate of powerfulness inwards this discipline, such equally an ETS plain bear witness or the GRE dependent test. The higher the correlation betwixt the established mensurate in addition to novel measure, the to a greater extent than faith stakeholders tin receive got inwards the novel assessment tool.
4. Formative Validity when applied to outcomes assessment it is used to assess how good a mensurate is able to supply information to help amend the computer programme nether study. Example: When designing a rubric for history i could assess student’s cognition across the discipline. If the mensurate tin supply information that students are lacking cognition inwards a surely area, for illustration the Civil Rights Movement, thus that assessment tool is providing meaningful information that tin live used to amend the course of instruction or computer programme requirements.
5. Sampling Validity (similar to content validity) ensures that the mensurate covers the wide attain of areas inside the concept nether study. Not everything tin live covered, thus items demand to live sampled from all of the domains. This may demand to live completed using a panel of “experts” to ensure that the content surface area is adequately sampled. Additionally, a panel tin help boundary “expert” bias (i.e. a bear witness reflecting what an private personally feels are the well-nigh of import or relevant areas). Example: When designing an assessment of learning inwards the theater department, it would non live sufficient to entirely comprehend issues related to acting. Other areas of theater such equally lighting, sound, functions of phase managers should all live included. The assessment should reverberate the content surface area inwards its entirety.
What are about ways to amend validity?
- Make surely your goals in addition to objectives are clearly defined in addition to ope-rationalized. Expectations of students should live written down.
- Match your assessment mensurate to your goals in addition to objectives. Additionally, receive got the bear witness reviewed past times faculty at other schools to obtain feedback from an exterior political party who is less invested inwards the instrument.
- Get students involved; receive got the students expect over the assessment for troublesome wording, or other difficulties.
- If possible, compare your mensurate alongside other measures, or information that may live available.
American Educational Research Association, American Psychological Association, & National Council on Measurement inwards Education. (1985). Standards for educational in addition to psychological testing. Washington, DC: Authors.
Cozby, P.C. (2001). Measurement Concepts. Methods inwards Behavioral Research (7th ed.). California: Mayfield Publishing Company.
Cronbach, L. J. (1971). Test validation. In R. L. Thorndike (Ed.). Educational Measurement (2nd ed.). Washington, D. C.: American Council on Education.
Moskal, B.M., & Leydens, J.A. (2000). Scoring rubric development: Validity in addition to reliability. Practical Assessment, Research & Evaluation, 7(10). [Available online: http://pareonline.net/getvn.asp?v=7&n=10].
The Center for the Enhancement of Teaching. How to amend bear witness reliability in addition to validity: Implications for grading. [Available online: http://oct.sfsu.edu/assessment/evaluating/htmls/improve_rel_val.ht