61 Teenagers’ use of emoticons in school writing. Due to the popularity of instant messaging and social networking sites among American teenagers, informal elements such as emoticons (e.g., the symbol “:)” to represent a smile) and abbreviations (e.g., “LOL” for “laughing out loud”) have worked their way into teenagers’ school writing assignments. In a survey cosponsored by the National Commission on Writing at the College Board, the Pew Internet and American Life Project (April 2008) interviewed 700 randomly selected U.S. teenagers by telephone on their writing habits. Overall, 448 of the teenagers admitted using at least one informal element in school writing assignments. Based on the survey results, construct a 99%

confidence interval for the proportion of all U.S. teenagers who have used at least one informal element in school writing assignments. Give a practical interpretation of the interval, one that is relevant to the National Commission on Writing at the College Board.