Usage of the major social media platforms varies by factors such as age, gender, and educational attainment. 28% of US adults use LinkedIn as their main social media platform. We speculate that this rate is different among college graduates. To investigate this idea, we took a random sample of 250 college graduates, and 32% stated using LinkedIn as their main social media platform. Which of the following is a complete definition of the unknown parameter ? Choice 1 of 4: The proportion of all US adults who use social media. Choice 2 of 4: The proportion of all US adults who use LinkedIn as their main social media platform. Choice 3 of 4: The proportion of all college graduates who use LinkedIn as their main social media platform. Choice 4 of 4: The sample proportion of college graduates who use LinkedIn as their main social media platform