The following data represent the marks obtained by $12$ students in $2$ tests, one held before coaching and the other after coaching:

$\backslash$table$[[$Test $1$:$,55,60,65,75,49,25,18,30,35,54,61,72],[$Test $2$:$,63,70,70,81,54,29,21,38,32,50,70,80]]$

Does the data indicate that the coaching was effective in improving the performance of students?