It is simply a two dimensional graph that plots % biting rate on the y-axis and log concentration on the x-axis.
- The % biting rate is:
$$[\text{% Biting rate}=\frac{\text{no. of human bites received (with repellant)}}{\text{no. of human bites received (without repellant)}}\times 100]$$
- The log concentration is:
$$\text{log concentration}=log_{10}{[\text{concentration (in ppm)}]}$$
To construct the B-R diagram:
1. Log concentrations of the repellant are plot along the x-axis at the appropriate intervals.
2. The % biting rates are plotted along the y-axis.
3. The percentage biting rates are plotted at corresponding concentrations.
The resulting curve should be a straight or almost straight line with a negative slope. The negative slope indicates that the % biting rate decreases as the concentration of repellant increases.
The B-R diagram is a useful tool for visually comparing the efficacy of different repellents and comparing the efficacy of the same repellant at different concentrations.