Question

Read and Analyze the review article about Principles and Methods of Validity and Reliability Testing of Questionnaires Used in Social and Health Science Researches given in the link below (Principles and Methods of Validity and Reliability Testing of Questionnaires Used in Social and Health Science Researches)
Q: Discuss about the reliability of a research instrument with the help of this review article in a brief manner with a maximum length of two pages. ( i need unique answer, don't copay and paste .don't use handwritting use keyboard)

Answer 1

Validity of an instrument/tool refers to the extent to which a data gathering instrument/tool measures what it is supposed to measure, i.e., the extent to which the instrument/tool obtain data that are relevant to what is being measured. The greater the validity of an instrument, the more confidence researcher can have that the instrument will obtain data that will answer the research question or test the research hypothesis.

There are following main approaches for establishing the validity of a tool.

1. Content validity The content validity of a tool is the extent to which the tool represents the phenomenon under study. It refers to the appropriateness of the content of an instrument.
2. Construct Validity It is an evaluation of the extent to which an instrument measures the theoretical construct that the investigator wishes to measure. A basic approach to establishing construct validity is the known group technique, in which the instrument is administered to several groups known to differ on a certain construct.
3. Criterion Validity Criterion validity of an instrument is determined by comparing the results of an instrument under testing with results of some “Gold Standard”, it refers to the measuring instrument that is being universally accepted or beyond doubt. Validity based on a gold standard (GS) is called as Criterion Validity.
4. Formative Validity Formative validity is used to assess how well a tool is able to provide information to help improve the program under study.

Reliability is also known as precision, reproducability, consistency and repeatability. Reliability is usually expressed as a number, called a coefficient. Reliability coefficient ranges between -1.00 to +1.00, with higher coefficients indicating higher levels of reliability. However, most of the instrument report reliability between 0.50 and 0.80.The three key aspects of reliability are stability, internal consistency, and equivalence.

1. Stability It is a measure of the instrument/tool to obtain similar results by administering the same test twice over a period of time to a group of individuals. The procedure used to assess the stability is the test-retest reliability.
2. Internal consistency Internal consistency reliability or scale homogeneity is the extent to which all items of an instrument measure the same variable. This type of reliability is appropriate only when the instrument is examining one concept or construct at a time. It is the most widely used approach to assess the reliability particularly in psychological instruments. The scales and tests that involve summing up of items are usually evaluated for their internal consistency, for example the scales measuring the attributes, attitudes etc. Split-half technique also called odd-even reliability yields the coefficient of internal consistency.  
3. Equivalence The equivalence approach is primarily used in observational measures. The commonest method used to establish the reliability in equivalence approach is Inter-rater / inter-observer reliability. Inter-rater reliability is a measure of reliability used to assess the degree to which different observers agree in their assessment decisions. A researcher uses an observation technique.