Which missing data technique is most appropriate when missing data are considered data missing completely at random $($MCAR$)?$

Multiple Cholce

Replacement

Weighting

Minimized deletion

Listwise deletion

Paliwise deletion

Consider the following array of numbers: $56777889991015192021.$ In the array provided, what is the mean? $($Round to the nearest whole number.$)$

Multiple Choice

Both $7$ and $9$

$11$

$9$

$7$

$15$