Which of the following is NOT a characteristic of a variable in a bivariate dataset?

In a bivariate dataset, variables are typically analyzed to understand the relationship between two distinct sets of data. Each variable has specific characteristics that aid in this analysis. The strength of the relationship refers to how closely the two variables are related, often measured through correlation coefficients. The trend of the data indicates the general direction in which the data points are moving, whether upward, downward, or remaining static, and is essential for interpreting the relationship accurately. The number of observations is crucial as it determines the sample size and reliability of the conclusions drawn from the data.

The method of classification used, however, is not a characteristic of the variables themselves but rather relates to how data is organized and presented. While different classification methods can influence the outcomes of an analysis, they do not define the inherent properties of the variables in a bivariate dataset. This is why identifying it as not a characteristic of the variables is the correct answer.