1/23/2019 VitalSource: Working with Political Science Research Methods
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Chapter 5 The Building Blocks of Social Scientific Research Measurement
Measurement involves deciding how to measure the presence, absence, or number of concepts in a research project. Reliability and validity of measures are key concerns.
A reliable measure yields a consistent, stable result as long as the concept being measured remains unchanged. Measurement strategies that rely on memories, for example, may be quite unreliable because the ability to remember specific information may vary depending on when the measurement is made and whether distractions are present.
Valid measures correspond well with the meaning of the concept being measured. Researchers often develop rather elaborate schemes to measure complex concepts.
Level of measurement is an important aspect of a measurement scheme. There are four levels of measurement. From lowest to highest, these levels are as follows: nominal, ordi
nal, interval, and ratio. Choosing the appropriate statistics for the analysis of data depends on knowing the level of measurement of your variables. Frequently a variable can be measured using a variety of schemes. Choosing the scheme that uses the highest level of measurement possible provides the most information and is the most precise measure of a concept. Researchers frequently recode data, thus changing the level of measurement of a variable.
Helpful Hints
Recoding Data There are two strategies for recoding data to combine or collapse categories of a measure:
1. Theoretical. Choose categories that are meaningfully distinct, where theory would tell you that the differences between the categories are important or where you can see that there are distinct clusters of scores or values. For example, when combining actual household income amounts into income levels, a researcher might consider what the official poverty level is and group all households with incomes below that level into the lowest income group.
2. Equally Sized Categories. Choose categories so that each category has roughly an equal number of cases. In addition, limit the number of categories so that each category has at least ten cases.