The influence of control group reproduction on the statistical power of the Environmental Protection Agency's Medaka Extended One Generation Reproduction Test (MEOGRT).
Because of various Congressional mandates to protect the environment from endocrine disrupting chemicals (EDCs), the United States Environmental Protection Agency (USEPA) initiated the Endocrine Disruptor Screening Program. In the context of this framework, the Office of Research and Development within the USEPA developed the Medaka Extended One Generation Reproduction Test (MEOGRT) to characterize the endocrine action of a suspected EDC. One important endpoint of the MEOGRT is fecundity of medaka breeding pairs. Power analyses were conducted to determine the number of replicates needed in proposed test designs and to determine the effects that varying reproductive parameters (e.g. mean fecundity, variance, and days with no egg production) would have on the statistical power of the test. The MEOGRT Reproduction Power Analysis Tool (MRPAT) is a software tool developed to expedite these power analyses by both calculating estimates of the needed reproductive parameters (e.g. population mean and variance) and performing the power analysis under user specified scenarios. Example scenarios are detailed that highlight the importance of the reproductive parameters on statistical power. When control fecundity is increased from 21 to 38 eggs per pair per day and the variance decreased from 49 to 20, the gain in power is equivalent to increasing replication by 2.5 times. On the other hand, if 10% of the breeding pairs, including controls, do not spawn, the power to detect a 40% decrease in fecundity drops to 0.54 from nearly 0.98 when all pairs have some level of egg production. Perhaps most importantly, MRPAT was used to inform the decision making process that lead to the final recommendation of the MEOGRT to have 24 control breeding pairs and 12 breeding pairs in each exposure group.
US Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Mid-Continent Ecology Division, Duluth, MN, USA. Electronic address: flynn.kevin@epa.gov.
Kevin
K
Flynn
Badger Technical Services, Duluth, MN, USA.
Joe
J
Swintek
US Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Mid-Continent Ecology Division, Duluth, MN, USA.
Rodney
R
Johnson
D000818:Animals; D035061:Control Groups; D052244:Endocrine Disruptors / Q000633:toxicity*; D004703:Endocrine System / Q000187:drug effects; D004787:Environmental Pollution / Q000032:analysis* / Q000706:statistics & numerical data; D005298:Fertility / Q000187:drug effects; D009990:Oryzias; D012098:Reproduction / Q000187:drug effects*; D014481:United States; D014484:United States Environmental Protection Agency / Q000706:statistics & numerical data*
D052244:Endocrine Disruptors
MEOGRT; Risk assessment; Statistical power; Study design