Find the mean of the following data set:
$8$8, $6$6
Find the mean of the following data set:
$6$6, $3$3
Find the mean of the following data set:
$8$8, $3$3, $4$4, $9$9, $6$6
Find the mean of the following data set:
$7$7, $12$12, $10$10, $9$9, $15$15, $11$11, $14$14, $8$8