As part of a national sleep survey, a random sample of adults was selected and surveyed about their physical activity and the number of hours they sleep each night. Of the 183 adults who exercised regularly (exercisers), 59 percent reported sleeping at least seven hours at night. Of the 88 adults who did not exercise regularly (non-exercisers), 52 percent reported sleeping at least seven hours at night. Which of the following is the most appropriate standard error for a conference interval for the difference in proportions of adults who sleep at least seven hours at night among exercisers and non-exercisers?