exams <-
structure(list(scores = c(57L, 66L, 69L, 71L, 72L, 73L, 74L, 
77L, 78L, 78L, 79L, 79L, 81L, 81L, 82L, 83L, 88L, 89L, 94L)), row.names = c(NA, 
-19L), class = c("tbl_df", "tbl", "data.frame"))