To calculate the percent error, we need to find the difference between the predicted number of attendees and the actual number of attendees, and then divide that difference by the predicted number of attendees. Finally, we multiply the result by 100 to convert it to a percentage.
1. Find the difference between the predicted number of attendees (275) and the actual number of attendees (265): 275 - 265 = 10.
2. Divide the difference by the predicted number of attendees: 10 / 275 = 0.03636363636 (rounded to 10 decimal places).
3. Multiply the result by 100 to get the percent error: 0.03636363636 * 100 = 3.636363636 (rounded to 10 decimal places).
Therefore, the percent error in their prediction is approximately 3.64%.
None of the provided responses match this calculation exactly. However, the closest option is "3.63%" which is rounded to two decimal places, so that would be the most appropriate response.