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Decamethylcyclopentasiloxane (D5) is a cyclic siloxane used in the production of industrial and consumer products. Four groups of 60 Fischer-344 female rats were analyzed for uterine endometrial adenocarcinoma (inhalation study with exposure levels in ppm/number of observed cases: 0/0, 10/1, 40/0, and 160/5) by exact regression (logistic, Poisson), the max poly-3 trend test, and a random effects probit model. When comparing the 160 ppm group to controls after 24 months, the incidence of adenocarcinomas was elevated (borderline significant); it was significant when all exposure levels were included. Four sets of (historical) control groups were formed, with varying heterogeneity. The effect of D5 was either significant or borderline significant when comparing all control sets to the 160 ppm group. When considering all exposure groups using any of the analysis methods, a significant effect was observed when the high dose group was included in the analysis; the effect was not significant when the high dose group was not included. The evidence tends to support the conclusion that D5 at the highest dose level (160 ppm) results in an increased incidence of adenocarcinomas. However, it is important to verify any potential effect through a biological investigation. (C) 2016 Published by Elsevier Inc.

This activity is an advanced version of the "Keep your eyes on the ball" activity by Bereska, et al. (1999). Students should gain experience with differentiating between independent and dependent variables, using linear regression to describe the relationship between these variables, and drawing inference about the parameters of the population regression line. Each group of students collects data on the rebound heights of a ball dropped multiple times from each of several different heights. By plotting the data, students quickly recognize the linear relationship. After obtaining the least squares estimate of the population regression line, students can set confidence intervals or test hypotheses on the parameters. Predictions of rebound length can be made for new values of the drop height as well. Data from different groups can be used to test for equality of the intercepts and slopes. By focusing on a particular drop height and multiple types of balls, one can also introduce the concept of analysis of variance. Key words: Linear regression, independent variable, dependent variables, analysis of variance

This group activity illustrates the concepts of size and power of a test through simulation. Students simulate binomial data by repeatedly rolling a ten-sided die, and they use their simulated data to estimate the size of a binomial test. They carry out further simulations to estimate the power of the test. After pooling their data with that of other groups, they construct a power curve. A theoretical power curve is also constructed, and the students discuss why there are differences between the expected and estimated curves.

Harvest frequency and burning can affect forage yield of monocultures of switchgrass (Panicurn virgutum L.), big bluestem (Andropogon gerurdii Vitman), and Indian grass [Sorghastrum nutuns (L.) Nash]. Current information is based largely on results from mixed stands. A field experiment was established in 1986, and from 1988 to 1991 treatments were applied with burning in March, April, or May plus an unburned control. Growing season yield was measured by harvesting 1 (June), 2 (June and July), or 3 (June, July, and August) times with unharvested control plots included. End-of-season standing crop from all plots was determined after plants became dormant. Treatments were applied to the same plots annually and were arranged in a split-split plot, randomized complete block design. The main plot was species, subplot was burn date, and sub-subplot was harvest frequency. Burning reduced yields (P<0.0l), and yields were lowest in plots burned in May. Burning reduced yields of Indian grass most (57%) and big bluestem least (15%). In 1989, plots harvested three times produced yields similar to plots harvested once for all species. By 1991, yields of plots harvested 3 times per growing- season were reduced (P=0.08) below those of plots harvested once. Yield response of species also varied across the study. Growing-season yields in 1991 were 113, 67, and 89% of 1989 yields for switch grass, big bluestem, and Indian grass, respectively. Regardless of burning and harvest frequency combination, switch grass produced as much or more herbage than the other species.