Cancer A group of investigators wishes to explore the relationship between the use of hair dyes and the development of breast cancer in females. A group of 1000 beauticians 30-39 years of age is identified and followed for 5 years. After 5 years, 20 new cases of breast cancer have occurred. Assume that breast- cancer incidence over this time period for an average woman in this age group is 7/1000. We wish to test the hypothesis that using hair dyes increases the risk of breast cancer. 7.27 Is a one-sided or two-sided test appropriate here?