Tag Archives: measurement

Test Validity

Validity is often seen as a close companion of reliability. Validity is the assessment of the evidence that indicates that an instrument is measuring what it claims to measure. An instrument can be highly reliable (consistent in measuring something) yet lack validity. For example, an instrument may reliably measure motivation but not valid in measuring income. The problem is that an instrument that measures motivation would not measure income appropriately.

In general, there are several ways to measure validity, which includes the following.

  • Content validity
  • Response process validity
  • Criterion-related evidence of validity
  • Consequence testing validity
  • Face validity

Content Validity

Content validity is perhaps the easiest way to assess validity. In this approach, the instrument is given to several experts who assess the appropriateness or validity of the instrument. Based on their feedback, a determination of the validity is determined.

Response Process Validity

In this approach, the respondents to an instrument are interviewed to see if they considered the instrument to be valid. Another approach is to compare the responses of different respondents for the same items on the instrument. High validity is determined by the consistency of the responses among the respondents.

Criterion-Related Evidence of Validity

This form of validity involves measuring the same variable with two different instruments. The instrument can be administered over time (predictive validity) or simultaneously (concurrent validity). The results are then analyzed by finding the correlation between the two instruments. The stronger the correlation implies the stronger validity of both instruments.

Consequence Testing Validity

This form of validity looks at what happened to the environment after an instrument was administered. An example of this would be improved learning due to test. Since the the students are studying harder it can be inferred that this is due to the test they just experienced.

Face Validity

Face validity is the perception that the students have that a test measures what it is supposed to measure. This form of validity cannot be tested empirically. However, it should not be ignored. Students may dislike assessment but they know if a test is testing what the teacher tried to teach them.


Validity plays an important role in the development of instruments in quantitative research. Which form of validity to use to assess the instrument depends on the researcher and the context that he or she is facing.

Levels of Measurement

A variable can be measured several different ways. This variety in variable measurement is broken down into four levels. These levels are nominal, ordinal, interval, and ratio. In this blog, I will talk about nominal and ordinal and I will address interval and ratio in the next post.

Nominal data is data that is broken into separate and discrete categories. The categories are mutually exclusive which means that no data can be in more than one category. Nominal data is also exhaustive in that all the data must go into one of the categories.  This is one of the weakest forms of measurement because differences within the category cannot be accounted for because all data is forced to conform to a category. Examples of nominal measurement would be gender because everyone who responds must be placed in one category or the other and there is no way for someone to be half male half female when using nominal classifications.

Ordinal measurement is used for ranking data.  At this level, data is still nominal but the order matters. An example would be class standing which is freshman, sophomore, junior,  and senior. The data is nominal in that there are categories but the order matters as a senior is a higher level in comparison to a freshman. There is still no attempt to differentiate within categories which weakens this level of measurement.

What level of measurement to use is dependent on what your research questions are. Research is guided by the question you ask.