Main points

1. Measurement is based on the inter-related processes of conceptualization and operationalization. Conceptualization is the process of defining concepts and specifying and defining any selected components or dimensions of concepts. Operationalization is the process of developing measurements for concepts or their dimensions.
   
2. Indicators are variables used to measure concepts or their dimensions. An indicator must have two or more attributes.
   
3. All indicators should be carefully analyzed to be sure they are appropriate in the cultural setting in which they will be used.
   
4. When possible, it is a good idea to use two or more indicators for measuring any concept or dimension.
   
5. There are four levels of measurement: nominal measurement indicates only that attributes differ in some way, as males vs. females; ordinal measurement indicates some order or ranking of attributes (high, middle and low social status, for example); interval measurement is based on numbers, but without an absolute zero point (temperature, intelligence); and ratio measurement is also numeric, but with a real or absolute zero point (age, size of a population).
   
6. Always use the highest level of measurement possible for any indicator. This will permit more powerful analyses of the resulting data.
   
7. A valid indicator   measures the intended concept and not something else. Ways of assessing the validity of an indicator include face or content validity, concurrent or criterion validity, and predictive validity.
   
8. A reliable measure provides consistent results from one time to another. Ways of testing the reliability of a measuring instrument include the test-retest method, the split-half or equivalent forms method, and use of Chronbach's alpha.
   
9. Reactivity refers to the extent to which the way data are collected affects the data obtained. Some methods of data collection are more reactive than others. Researchers seek to minimize reactivity effects in the collection of data.
   
10. Investigators are responsible for adhering to ethical standards in collecting and analyzing data and in how results are reported.
    
11. Two basic ethical guidelines are: (1) participation in research must be voluntary; and (2) participants should not be harmed.