Each interval contributes an area determined by two measurements: the distance between neighboring data points and the average of their function values. Multiplying the interval width by this endpoint average produces one trapezoid’s estimated area. Adding the contributions from all consecutive intervals yields the cumulative quantity represented by the measured curve.
Smaller intervals place trapezoid boundaries closer together, so each straight-line approximation covers a shorter portion of the curve. This generally reduces the discrepancy between the estimated shape and the measured trend across the interval. Consequently, collecting or using more closely spaced biological measurements can improve the numerical estimate of cumulative exposure, growth, or concentration.
An exact equation permits integration from a defined mathematical expression, whereas this method works directly with discrete measurements. That distinction matters when biological observations are recorded at sampling times without a known equation describing the entire curve. The calculation therefore depends on the available endpoint values and interval widths rather than on an analytically specified function.
First, arrange the measured values according to their corresponding interval positions, such as successive times. Next, calculate each interval width and average the two values at its endpoints. Multiply those quantities to obtain each trapezoid’s contribution, then sum all contributions. The resulting total estimates the area represented by the complete set of measurements.
It is useful when a study produces discrete measurements but the desired result is cumulative rather than a single observation. For example, measurements taken across time can support an estimate of exposure over that period. The same approach can convert a series of biological readings into an area-under-the-curve value for quantitative analysis.
The method can be applied to measured growth curves and concentration curves, as well as data representing exposure over time. In each case, the estimated area summarizes the accumulated behavior across the selected interval. This allows investigators to compare or interpret a set of discrete biological observations through one cumulative quantity rather than isolated measurements.