In a 1985 study of the relationship between contraceptive  use and infertility, 89 of 283 infertile women, compared with  640 of 3833 control (fertile) women, had used an intrauterine device (IUD) at some time in their lives [43]. *13.1 Use the normal-theory method to test for significant  differences in contraceptive-use patterns between the two  groups