Cronbach’s alpha is the most widely used objective measure of reliability of scales. Therefore, is it a good measure to tell us about the reliability of a questionnaire regardless of the discipline/ field of study?
Hi Achinthya,
Yes, you can perform a Cronbach's alpha test on your questionnaire. However, it is not the only measure to validate a questionnaire. The test tells you that your items measure the same concept (or not), it's called a measure of internal consistency. To validate a questionnaire, you need to test several psychometrical properties (e.g., content validity, construct validity, test-retest, ...). I suggest you to have a look on this topic in RG, especially Paul's answer: https://www.researchgate.net/post/What_is_the_best_method_to_validate_a_questionnaire_based_on_a_5_point_Likert_scale
It is a long work to create a questionnaire, good luck for your project.
I hope these elements will help,
Julian
Cronbach's alpha coefficient is used for measuring the validity and reliability (internal and external) of questionnaire in the scientific research, In order to know the validity and reliability of the study scale within the questionnaire, this method should be used
yes of course you cn use it for each measure in you questionnaire
I think the Cronbach alpha can only "validate" the fact that the items may be measuring a certain construct(s) (reliability). Now, whether that specific construct is initially what the questionnaire meant to measure (validity) is another question.
Cronbach's alpha CANNOT speak to the validity of an instrument only its internal consistency, which can be used to infer reliability. Reliability refers to the consistency of a measure (whether the results can be reproduced under the same conditions). It is concerned with measurement error. Validity refers to the extent that a a measure is actually measuring the intended construct (whether the results really do represent what they are supposed to measure).
These two terms, reliability and validity, are often used interchangeably when they are not related to statistics. When critical readers of statistics use these terms, however, they refer to different properties of the statistical or experimental method.
Reliability is another term for consistency. If one person takes the same personality test several times and always receives the same results, the test is reliable.
A test is valid if it measures what it is supposed to measure. If the results of the personality test claimed that a very shy person was in fact outgoing, the test would be invalid.
Reliability and validity are independent of each other. A measurement maybe valid but not reliable, or reliable but not valid. Suppose your bathroom scale was reset to read 10 pound lighter. The weight it reads will be reliable(the same every time you step on it) but will not be valid, since it is no treading your actual weight (https://web.cortland.edu/andersmd/STATS/valid.html).
Cronbach's alpha CANNOT be used to infer anything useful about validity only internal consistency or reliability.
Reliability refers to the consistency of a measure. Psychologists consider three types of consistency: over time (test-retest reliability), across items (internal consistency), and across different researchers (inter-rater reliability). Another kind of reliability is internal consistency, which is the consistency of people’s responses across the items on a multiple-item measure. In general, all the items on such measures are supposed to reflect the same underlying construct, so people’s scores on those items should be correlated with each other. Cronbach's alpha measures internal consistency.
As an absurd example, imagine someone who believes that people’s index finger length reflects their self-esteem and therefore tries to measure self-esteem by holding a ruler up to people’s index fingers. Although this measure would have extremely good test-retest reliability, it would have absolutely no validity. The fact that one person’s index finger is a centimeter longer than another’s would indicate nothing about which one had higher self-esteem. (see https://opentext.wsu.edu/carriecuttler/chapter/reliability-and-validity-of-measurement/)
Cronbach alpha can only be used to establish the internal consistency of an instrument. That is how each of the items correlates with each other and at the same time produces similar or same results repeatedly. However, validity intends to measure the contents accurately. @Michael James Ireland, I agreed with your submission.
Meanwhile in addition to @Michael contribution a good instrument should be valid and also reliable to be capable of collecting data that can be generalized from samples in a population.
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