The test interval for TIM is the period immediately after a test day through the following test day and is composed of two equal parts (2). Production credits for the first half of the test period are assumed to be the same as the earlier test day yield, and credits for the last half are assumed to be the same as the later test day yield. For first and last test intervals, yield credits are calculated the same as for the method. During the 1970s, TIM was improved by adjusting credits for the first and second test inter-vals for the nonlinear shape of the lactation curve and by adjusting the last test for a continuation of the expected decline (11). Those adjustments eliminated biases from overestimation of the credits for first and last test intervals and from an underestimation of the credits for the second test interval.
Comparison of Test Interval and Best Prediction Methods for Estimation of Lactation Yield from Monthly, a.m.–p.m., and Trimonthly Testing (PDF Download Available). Available from: https://www.researchgate.net/publication/13221765_Comparison_of_Test_Interval_and_Best_Prediction_Methods_for_Estimation_of_Lactation_Yield_from_Monthly_am-pm_and_Trimonthly_Testing [accessed May 8, 2016].