What is the difference between reliability and validity? | MyTutor
1 Pre-requisites; 2 Relationship between reliability and validity; 3 Data analysis exercises; 4 See also; 5 References; 6 Bibliography; 7 External. As mentioned in Key Concepts, reliability and validity are closely related. To better understand this relationship, let's step out of the world of testing and onto a . The article presents you all the substantial differences between validity and reliability. Validity of the measuring instrument represents the.
Classroom Assessment | Basic Concepts
Simply, it measures the point to which differences discovered with the scale reflect true differences, among objects on the characteristics under study, instead of a systematic and random error. To be considered as perfectly valid, it should not possess any measurement error.
There are three types of validity, which are: Otherwise known as face validity, it is the point to which the scale provides adequate coverage of the subject being tested. The type of validity which gauges the performance of measuring instrument, i.
The criterion should be relevant, unbiased, reliable, etc. Construct validity in a measure refers to the extent to which it adheres to estimated correlations with other theoretical suppositions. Convergent Validity Nomological Validity Definition of Reliability Reliability is used to mean the extent to which the measurement tool provides consistent outcomes if the measurement is repeatedly performed.
Relation between Validity and Reliability of a Test
To assess reliability approaches used are test-retest, internal consistency methods, and alternative forms. There are two key aspects, which requires being indicated separately are: Degree of stability can be checked by making a comparison of the results of repeated measurement. Equivalence can be gauged when two researchers compare the observations of the same events.
Systematic errors do not affect reliability, but random errors lead to inconsistency of the results, thus lower reliability. When the research instrument conforms to reliability, then one can be sure that the temporary and situational factors are not interfering.
What is the difference between reliability and validity?
Reliability can be improved by way of: Here, you can clearly see that reliability is directly related to the variability of your measure.
The third scenario shows a case where your hits are spread across the target and you are consistently missing the center. Your measure in this case is neither reliable nor valid.
Finally, we see the "Robin Hood" scenario -- you consistently hit the center of the target. Your measure is both reliable and valid I bet you never thought of Robin Hood in those terms before.
Another way we can think about the relationship between reliability and validity is shown in the figure below. Here, we set up a 2x2 table. The columns of the table indicate whether you are trying to measure the same or different concepts. The rows show whether you are using the same or different methods of measurement.
Reliability and validity - Wikiversity
Imagine that we have two concepts we would like to measure, student verbal and math ability. Furthermore, imagine that we can measure each of these in two ways. Second, we can ask the student's classroom teacher to give us a rating of the student's ability based on their own classroom observation.
The first cell on the upper left shows the comparison of the verbal written test score with the verbal written test score. But how can we compare the same measure with itself? We could do this by estimating the reliability of the written test through a test-retest correlation, parallel forms, or an internal consistency measure See Types of Reliability. What we are estimating in this cell is the reliability of the measure.
The cell on the lower left shows a comparison of the verbal written measure with the verbal teacher observation rating. Because we are trying to measure the same concept, we are looking at convergent validity See Measurement Validity Types.
The cell on the upper right shows the comparison of the verbal written exam with the math written exam. Here, we are comparing two different concepts verbal versus math and so we would expect the relationship to be lower than a comparison of the same concept with itself e. Thus, we are trying to discriminate between two concepts and we would consider this discriminant validity.