The graph shows the effectiveness of two types of condoms and the contraceptive pill at preventing pregnancies with perfect use and with typical use, that is, with possible human error. Which statement is correct about the data shown? (A) The female condom is more effective at preventing pregnancies than the contraceptive pill. (B) The effectiveness of all methods is lower with typical use compared to perfect use. (C) Male condoms are more effective at preventing pregnancy with typical use than with perfect use. Or (D) the contraceptive pill is the least effective method of contraception.
This question asks us to interpret a column graph that compares three methods of contraception. Let’s start by examining the axes of the graph to get a better understanding of the data. The 𝑥-axis displays the labels for the three methods of contraception. Moving from left to right along the 𝑥-axis, we can see that the first method is the contraceptive pill, which is a hormonal method of contraception. This means it involves the artificial release of estrogen and/or progesterone into a female’s bloodstream.
The second and third methods displayed along the 𝑥-axis are male condoms and female condoms. Condoms are a barrier method of contraception, which means they involve a structure that physically blocks the sperm. The 𝑦-axis of the graph displays the percentage of pregnancies that were prevented by each method of contraception, or its effectiveness. We can see that there are two columns for each method of contraception. The legend tells us that the pink column, which appears first for each method, gives its effectiveness with perfect use, whereas the purple column, which appears second for each method, gives its effectiveness with typical use.
You may remember that perfect use describes the effectiveness of contraception when it is used exactly as instructed, whereas typical use describes the effectiveness of contraception when used with normal human error, for example, forgetting to take a contraceptive pill or not following the instructions exactly on condoms. There is a distinct pattern in the data. If you haven’t already picked up on it, pause the video and see if you can spot it.
We can see that for each method of contraception, the perfect use column is higher than the typical use column, indicating that for each method shown on the graph, perfect use is more effective than typical use. This pattern makes total sense because with perfect use, pills and condoms are being used exactly as they were designed, with no error. However, this pattern does not hold for long-lasting reversible methods, such as intrauterine devices, or IUDs. These methods have nearly identical perfect use and typical use because after being administered by a medical professional, they don’t require users to follow any instructions.
Now, let’s return to the answer choices to determine the correct statement about the data. The pattern we found in the data — that is, perfect use is more effective than typical use — is just another way of stating this answer choice. Therefore, the correct statement about the data shown in this graph is the effectiveness of all methods is lower with typical use compared to perfect use.