During each of four experiments on the use of carbon tetrachloride as a worm killer, ten...

During each of four experiments on the use of carbon tetrachloride as a worm killer, ten rats were infested with larvae (Armitage 1983). Eight days later, five rats were treated with carbon tetrachloride; the other five were kept as controls. After two more days, all the rats were killed and the numbers of worms were counted. The table below gives the counts of worms for the four control groups. Significant differences, although not expected, might be attributable to changes in experimental conditions. A finding of significant differences could result in more carefully controlled experimentation and thus greater precision in later work. Use both graphical techniques and the F test to test whether there are significant differences among the four groups. Use a nonparametric technique as well.