Question

How does reliability differ from validity? Give examples of each.

Your firm is conducting a study in which the key dependent variable is annual sales. The firm plans to compare sales among different types of customers with whom the firm does business. What type of scale should be used to measure annual sales? Why?

Answer 1

Validity: It is the most important yardstick that signals the degree to which research instrument gauges, what it is supposed to measure.

Reliability is used to mean the extent to which the measurement tool provides consistent outcomes if the measurement is repeatedly performed. To assess reliability approaches used are test-retest, internal consistency methods, and alternative forms.

Example: if a test is designed to assess the learning in the biology department, then that test must cover all aspects of it including its various branches like zoology, botany, microbiology, biotechnology, genetics, ecology, etc., or at least appear to cover.

Example: If the problem-solving skills of an individual are being tested, one could generate a large set of suitable questions that can then be separated into two groups with the same level of difficulty, and then administered as two different tests. The comparison of the scores from both tests would help in eliminating errors if available.

The fundamental differences between validity and reliability:

1. The degree to which the scale gauges, what it is designed to gauge, is known as validity. On the other hand, reliability refers to the degree of reproducibility of the results, if repeated measurements are done.
2. When it comes to the instrument, a valid instrument is always reliable, but the reverse is not true, i.e. a reliable instrument need not be a valid instrument.
3. While evaluating multi-item scale, validity is considered more valuable in comparison to reliability.
4. One can easily assess the reliability of the measuring instrument, however, to assess validity is difficult.
5. Validity focuses on accuracy, i.e. it checks whether the scale produces expected results or not. Conversely, reliability concentrates on precision, which measures the extent to which scale produces consistent outcomes