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What are the Psychometric Properties of a Research Instrument?

Here is a differentiation of reliability and validity as applied to the preparation of research instruments. 

One of the most difficult parts in research writing is when the instrument’s psychometric properties are scrutinized or questioned by your panel of examiners. Psychometric properties may sound new to you, but they are not actually new.

In simple words, psychometric properties refer to the reliability and validity of the instrument. So, what is the difference between the two?

Reliability refers to the consistency while validity refers to the test results’ accuracy. An instrument should accurately and dependably measure what it ought to measure. Its reliability can help you have a valid assessment; its validity can make you confident in making a prediction.

Instrument’s Reliability

How can you say that your instrument is reliable? Although there are many types of reliability tests, what is more usually looked at is the internal consistency of the test. When presenting the results of your research, your panel of examiners might look for the results of the Cronbach’s alpha or the Kuder-Richardson Formula 20 computations. If you cannot do the analysis by yourself, you may ask a statistician to help you process and analyze data using a reliable statistical software application.

correlation

But if your intention is to determine the inter-correlations of the items in the instrument and if these items measure the same construct, Cronbach’s alpha is suggested. According to David Kingsbury, a construct is the behavior or outcome a researcher seeks to measure in the study. This is often revealed by the independent variable.

When the inter-correlations of the items increase, the Cronbach’s alpha generally increases as well. The table below shows the range of values of Cronbach’s alpha and the corresponding descriptions on internal consistency.

Cronbachs alpha

(Note: The description is not officially cited and taken only from Wikipedia, but you may confer with your statistician and your panel of examiners. If the value of alpha is less than .05, the items are considered poor and must be omitted).

Instrument’s Validity

There are many types of validity measures. One of the most commonly used is the construct validity. Thus, the construct or the independent variable must be accurately defined.

To illustrate, if the independent variable is the school principals’ leadership style, the sub-scales of that construct are the types of leadership style such as authoritative, delegative and participative.

The construct validity would determine if the items being used in the instrument have good validity measures using factor analysis and each sub-scale has a good inter-item correlation using Bivariate Correlation. The items are considered good if the p-value is less than 0.05.

References:

1. Kingsbury, D. (2012). How to validate a research instrument. Retrieved October 16, 2013, from http://www.ehow.com/how_2277596_validate-research-instrument.html

2. Grindstaff, T. (n.d.). The reliability & validity of psychological tests. Retrieved October 16, 2013, from http://www.ehow.com/facts_7282618_reliability-validity-psychological-tests.html

3. Renata, R. (2013). The real difference between reliability and validity. http://www.ehow.com/info_8481668_real-difference-between-reliability-validity.html

4. Cronbach’s alpha. Retrieved October 17, 2013, from http://en.wikipedia.org/wiki/Cronbach%27s_alpha

© 2013 October 17 M. G. Alvior

By Alvior, Mary G.

Dr. Mary Gillesania Alvior has PhD. in Curriculum Development from West Visayas State University. She earned her Master of Arts in Teaching English Language at De La Salle University, Manila as CHED scholar. She worked at the Royal Commission for Jubail and Yanbu in Saudi Arabia as an English instructor and curriculum developer. Her committee was responsible for the development of an english curriculum based on the Common European Framework of Reference for Languages (CEFR) and used the English Language Proficiency Exams as assessment tools. In 2016, she moved to Thailand and taught at the St. Theresa International College. She was able to teach English and Education courses to college and MA students. In the Diploma in Teaching course, she was able to observe different classes in Thailand. From pre-school to high school classes, from private to government schools, from small private schools to the most elite schools, and from local schools to international schools. Her students came from 14 countries and some of them are retired from famous organizations and graduates of Oxford University, McGill University, National University of Singapore, MIT, British Columbia, among others. Her experiences in a multi-cultural environment made her exposed to different curricula and programs abroad. Curricular programs that are industry-related, innovative, and follow global standards. The kind of programs that are much needed by developing countries.

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