Efficiency of Linear Search

How much number of comparisons is there in this search in searching for a particular element?

The number of comparisons based upon where the record along the argument key appears in the array. If record is at the primary place, number of comparisons is '1', if record is at last position 'n' comparisons would have to make.

If it is evenly likely for that the record can seem at any position in the array, then, a successful search will take (n+1)/2 comparisons & an unsuccessful search will take 'n' comparisons.