In terms of symbols, let D(1i) represent the linear trend for a given angle. For the hypothetical data contained in Table 14.4, Table 14.5 gives an appropriate and substantively interesting set of D variables. The D variables (rather than the raw data itself) is used because of the benefits and flexibility gained from analyzing the D variables directly (rather than indirectly as we did with the Table 14.4 data).
References
Maxwell, S. E., Delaney, H. D., & Kelley, K. (2018). Designing experiments and analyzing data:
A model comparison perspective (3rd ed.). New York, NY: Routledge.