Question

Power lines and cancer (4.2, 4.3) Does living near power lines cause leukemia in children? The National Cancer Institute spent 5 years and $5 million gathering data on this question. The researchers compared 638 children who had leukemia with 620 who did not. They went into the homes and measured the magnetic fields in children’s bedrooms, in other rooms, and at the front door. They recorded facts about power lines near the family home and also near the mother’s residence when she was pregnant. Result: no connection between leukemia and exposure to magnetic fields of the kind produced by power lines was found.7

(a) Was this an observational study or an experiment? Justify your answer.

(b) Does this study show that living near power lines doesn’t cause cancer? Explain.

Answer 1

Solution

Part (a)

This was an observational study and not an experiment. Answer 1

[Because only two types of children were observed for incidence of leukemia vis-à-vis exposure to magnetic field.

Had the researchers, picked up a group of children with no history of leukemia, divided them into two groups, exposed one group to magnetic field (treatment group) and the other group unexposed to magnetic field (control group) and evaluated the incidence of leukemia in both groups, that would be an experiment.   

Part (b)

The given statement is far-fetched from the scope of the study. The study is confined to children and one type of cancer, namely leukemia.

So, generalizing over general population and also over cancer as a whole would not be justified. Answer 2

DONE