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As part of preliminary analyses, researchers analyze each important variable separately to understand its distribution by creating histograms and computing central tendency and variability. However, this step is not necessary for manipulated independent variables because their distribution is predetermined by the researcher.

Single Variable Analysis

An example of analyzing a single variable involves a distribution of self-report happiness ratings on a 1-to-10-point scale. The distribution might be unimodal and negatively skewed, with a mean of $$8.25$$ and a standard deviation of $$1.14$$. This indicates that most participants rated themselves highly on the happiness scale, while a small number reported noticeably lower ratings.

Self-Report Happiness Ratings Example

When conducting preliminary analyses, it is unnecessary to analyze the distribution of a manipulated independent variable because its distribution is predetermined by the researcher.

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