Chapter 13, Problem 73H

DDT is a pesticide that has been banned from use in the United States and most other areas of the world. It is quite

effective, but persisted in the environment and over time became seen as harmful to higher-level organisms. Famously, egg

shells of eagles and other raptors were believed to be thinner and prone to breakage in the nest because of ingestion of DDT

in the food chain of the birds.

An experiment was conducted on the number of eggs (fecundity) laid by female fruit flies. There are three groups of flies.

One group was bred to be resistant to DDT (the RS group). Another was bred to be especially susceptible to DDT (SS).

Finally there was a control line of non-selected or typical fruitflies (NS). Here are the data:

RS	SS	NS	RS	SS	NS
12.8	38.4	35.4	22.4	23.1	22.6
21.6	32.9	27.4	27.5	29.4	40.4
14.8	48.5	19.3	20.3	16	34.4
23.1	20.9	41.8	38.7	20.1	30.4
34.6	11.6	20.3	26.4	23.3	14.9
19.7	22.3	37.6	23.7	22.9	51.8
22.6	30.2	36.9	26.1	22.5	33.8
29.6	33.4	37.3	29.5	15.1	37.9
16.4	26.7	28.2	38.6	31	29.5
20.3	39	23.4	44.4	160.9	42.4
29.3	12.8	33.7	23.2	16.1	36.6
14.9	14.6	29.2	23.8	10.8	47.4
27.3	12.2	41.7

Table 13.29

The values are the average number of eggs laid daily for each of 75 flies (25 in each group) over the first 14 days of their

lives. Using a 1% level of significance, are the mean rates of egg selection for the three strains of fruitfly different? If so,

in what way? Specifically, the researchers were interested in whether or not the selectively bred strains were different from

the nonselected line, and whether the two selected lines were different from each other.

Here is a chart of the three groups:

Figure