Reliability and Validity in Research

Keywords: article on dependability, validity in public research

The two most important and important characteristics of any measurement procedure are trustworthiness and validity. Trustworthiness and validity instructs us whether a study being carried out studies what it is meant to review, and if the procedures used are constant. These two rules are mentioned below.


Joppe (2000) defines consistency as the level to which results are consistent as time passes and a precise representation of the total population under review is referred to as reliability if the results of a study can be reproduced under a similar methodology, then your research instrument is considered to be reliable. It is the magnitude to which a questionnaire, test, observation or any measurement technique produces the same results on repeated tests. It's important to note the thought of replicability or repeatability of results or observations. Reliability relates to figures or scores rather than humans. Therefore, it would be wrong in neuro-scientific research to say that someone is reliable. Take for illustration, in a mathematics quiz competition for academic institutions. The degree to that your results of the panel of judges for each and every contestant agree can be an indication of consistency. Similarly, the degree to which an individual's reactions (i. e. , their results) on a study would stay the same as time passes is also a way of measuring reliability.

A solution can be reliable without being valid. A solution cannot be valid without having to be reliable. Consider a tape guideline that always actions my elevation as 175cm, taller than my true level. This tape-rule (though invalid as it incorrectly assesses height) is properly reliable as it regularly measures my height as 175cm, taller than I must say i are. A study example of this phenomenon will be a questionnaire designed to evaluate the impact of corporate sociable responsibility on worker commitment that asked questions such as, "Do you like to swim?", "What do you want to eat more, pizza or hamburgers?" and "What is your favorite shade?". As you can readily think about, the reactions to these questions would probably remain stable over time, thus, demonstrating highly reliable scores. However, will be the questions valid when one is attempting to evaluate impact of corporate and business public responsibility on worker commitment? Of course not, as they have nothing to do with the research purpose.

Assessing the Four Types of Reliability

There are four aspects of reliability, particularly: equivalence, steadiness and internal persistence (homogeneity). It's important to comprehend the variation between these three as it will guide one in the proper assessment of reliability given the study protocol.

Test-Retest dependability (also known as Stability): This right answers the question, "Will the results or results be secure over the time a strategy is administered". Steadiness is said to arise when the same or similar scores are obtained with repeated assessment with the same band of respondents. Balance is assessed by way of a test-retest procedure which involves administering the same measurement tool to the same individuals under the same conditions after some period of time. The consistency coefficient is likely to be highly correlated. For example, if a class achievement test is administered today and the test is given two weeks later, it is likely to have a reliability coefficient of r = 0. 75 or even more.

Parallel forms dependability (also known as Equivalence): This answers the question, "Will be the two kinds of the test or measure equivalent?" If different forms of the same test or strategy are implemented to the same group; one would expect that the reliability coefficient will be high. Equivalence measures the level of agreement between two or more equipment that are administered at nearly the same point in time. It is measured by having a parallel forms procedure in which one administers choice forms of the same solution to either the same group or different group of respondents. This administration of the many forms occurs at the same time or following time delay. The higher the amount of correlation between your two forms, the more equivalent they are really.

Internal consistency consistency or homogeneity answers the question, "How well does each item measure the content or construct under consideration?" It really is an sign of dependability for a test or measure which is given once. One needs the relationship between reactions to each test item to be highly correlated with the full total test score. For instance, an employee job satisfaction (attitude range) or a class achievements test which is implemented once. Internal regularity is believed via the split-half stability index, coefficient alpha (Cronbach, 1951) index or the Kuder-Richardson formula 20 (KR-20) (Kuder & Richardson, 1937) index.

Inter-rater consistency: Different raters, by using a common ranking form, measure the object of interest consistently. Inter-rater arrangement right answers the question, "Will be the raters constant in their scores?" One expects that the reliability coefficient will be high, if the observers ranked similarly. For instance, three older sales trainers score the closing skills of a novice sales consultant or master professors rating the teaching effectiveness of a first or second yr teacher.

At this aspect, it's important to understand the two main questions consistency really helps to answer;

  • What is known as a 'good' or 'good' value? and
  • How does one increase the reliability of an survey tool?

The basic convention in research has been recommended by Nunnally and Bernstein (1994) who declare that one should strive for reliability values of. 70 or higher. Reliability values increase as test duration enhances (Gulliksen, 1950) That's, the greater items you have in your level to gauge the construct appealing the greater reliable your level will become.

Various indices for examining the trustworthiness of options have been proposed. We shall take a look at them in relationships to the type of reliability they evaluate.

Various Consistency Indices

Parallel varieties procedure: This process steps Equivalence. Here, one administers substitute types of the same solution to either the same group or different band of respondents. This supervision of the various forms occurs at the same time or following a while delay. The bigger the amount of correlation between your two forms, the greater equivalent they are really. In practice the parallel varieties procedure is seldom put in place, as it is difficult, if not impossible, to validate that two lab tests are indeed parallel (i. e. , have equal means, variances, and correlations with other methods). Indeed, it is difficult enough to get one well-developed device to measure the construct appealing let alone two. Another situation where equivalence will be important is when the measurement process entails subjective judgments or ratings being created by several person.

Test-retest process: This is utilized to measure balance. It requires administering the same way of measuring instrument to the same individuals under the same conditions after some period of time. Test-rest stability is approximated with correlations between the ratings at Time 1 and the ones at Time 2 (to Time x). Two assumptions underlie the utilization of the test-retest method. The first required assumption is that the feature that is assessed will not change over the period of time. The next assumption is the fact the period of time is long enough that the respondents' memory of taking the test at Time 1 will not influence their results at the next and following test administrations.

Split-half dependability index: This index is utilized in estimating inner steadiness. The split-half estimate entails dividing in the test into two parts (e. g. , peculiar/even items or first fifty percent of the items/second half of the things), administering the two varieties to the same band of individuals and correlating the replies.

Other indices for calculating internal consistency will be the coefficient alpha (Cronbach) index, the Kuder-Richardson formula 20 (KR-20) and the (Kuder & Richardson, 1937) index. This indices signify the average of most possible split-half quotes. The difference between your two is when they would be used to assess reliability. Specifically, coefficient alpha is normally used during scale development with items which have several response options (i. e. , 1 = strongly disagree to 5 = strongly acknowledge) whereas KR-20 can be used to estimate stability for dichotomous (i. e. , Yes/No; True/Incorrect) response scales.


Validity examines how truthful the study results are. It is the extent to which the instrument measures what it purports to measure. In other words, does the research instrument enable you going to "the bull's eyeball" of your quest object? For example, a test that is used to screen people for M. sc admissions into a UK college or university is valid if its scores are immediately related to future academics performance of students either in research thesis or course work. Researchers generally determine validity by requesting a series of questions, and can often look for the answers in the study of others.

There are numerous kinds of validity. They include: content validity, face validity, criterion-related validity (or predictive validity), build validity, factorial validity, concurrent validity, convergent validity and divergent (or discriminant validity). The four most mentioned types will be discussed here.

Construct validity:-

Wainer and Braun (1998) identify the validity in quantitative research as "build validity". The construct is the initial concept, notion, question or hypothesis that establishes which data is to be gathered and exactly how it is to be gathered.

Construct validity is the degree to which an instrument measures the characteristic or theoretical construct that it is intended to evaluate. For instance, if one were to build up a musical instrument to measure intellect that does indeed indeed measure IQ, then this test is construct valid.

Content validity:-

This pertains to the degree to that your instrument totally assesses or measures the construct of interest. For instance, say we have been interested in evaluating employees' attitudes toward a training program in a organization. We would want to ensure that our questions fully represent the area of behaviour toward working out program. The introduction of a content valid device is typically achieved by a rational examination of the device by raters (preferably 3 to 5 5) familiar with the construct of interest ( Michael J. Miller 2004)

Face validity:-

This an element of content validity and is set up when a person reviewing the tool concludes that it measures the quality or trait appealing. For instance, when a quiz in this category comprised items which asked questions regarding research methods you would probably conclude that it was face valid. In short, it looks as if it is definitely calculating what it was created to measure.


Criterion related validity is evaluated when one is interested in deciding the partnership of scores over a test to a particular criterion. An example is that ratings on employment test for fresh graduate should be related to relevant standards such as junior service corps completion(for students in Nigeria), category of level, etc. Conversely, an instrument that measures coloring inclinations would most assuredly illustrate inadequate criterion-related validity regarding graduate job location.


In conclusion, it is important to notice that one's ability to answer a study question is only as good as the musical instruments developed or ones approach to data collection. A well-developed study device will better give a researcher with quality data with which to answer a question or solve a problem. Finally, recall that for something to be valid it must be reliable but it must evaluate what it is intended to measure.

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