dr.susan.carroll@snet.net

### Measuring dissertation variables and selecting instruments

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When we collect information about people, objects and events, we must turn that information into numbers so that we can measure it. Measuring dissertation variables and selecting instruments are among the most challenging parts of the doctoral process. The following descriptive information is provided with the intention of helping you to do a good job with these tasks.

Data are derived from characteristics about individuals, objects or events. These characteristics are called variables. You attach numbers to your dissertation variables in an effort to measure them and apply statistics to them when you use your instruments.

Categorical variables have different categories and each category takes on a whole number or integer to represent it. The number that is assigned to the category does not have any meaning. A simple example of a categorical variable is Gender [male=0 and female=1]

Variables that are quantitative are classified as either discrete or continuous. They can take on numbers or integers that represent some degree of the variable. For example, the variable of household size for the families can be 1 (one person), 2 and up to double digits for a big family.

There are four scales of measurement used to assign numbers to your variables.

1. Nominal

2. Ordinal

3. Interval

4. Ratio

Finally, you have to choose data collection instruments which will assign numbers to your variables. You will be asked about their validity and reliability .

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