A researcher is interested in studying the relationship between the beats per minute of a song and running speed (while listening to the song). She recruits 5 runners and puts an app on their phone that records the beats per minute and running speed of every song they listen to while running for a period of 1 week. She collects the resulting data. Each runner submitted data for a different number of songs, depending on how much time they ran during the week. Runner 1 had 55 songs, runner 2 had 3 songs, runner 3 had 72 songs, runner 4 had 78 songs, and runner 5 had 10 songs. Her resulting dataframe has 218 songs across the 5 runners (55 + 3 + 72 + 78 + 10). Using data for these 218 songs across all runners she fits a simple linear regression model, regressing running speed during the song on the beats per minute of the song. Based on this information alone, which assumption of linear regression modeling is violated? A researcher is interested in studying the relationship between the beats per minute of a song and running speed (while listening to the song). She recruits 5 runners and