Understanding Numbers

Topic of birth control came up with my friends, and we talked about effectiveness of condoms and IUD. While we all seemed to agree that IUD is the most effective and economical option, one friend pointed out that we should really try to understand the meaning of the statistics that evidence IUD effectiveness. They say that while condoms are effective 95% of time, and IUD for 99%, we shouldn't jump to conclusion that IUD is the superior method of birth control--rather, the 95% statistics for condoms count for cases where condoms are misused, and the number itself doesn't do justice to the effectiveness of condoms. This made me think about how I should present numbers and how I should interpret the numbers, depending on my intentions and goals.