Answer to Question #73686 in Algorithms for L Anderson Jr

Question

Consider an array of prime integers in the range [1...20] with the entries randomly distributed. Find the average number of comparisons for a sequential search in the array.

Answer 1

Answer on Question #73686 - Algorithms
Prime integers in the range [1...20] are 2, 3, 5, 7, 11, 13, 17, 19 (8 numbers).
The sequential search in a randomly distributed array for any present element will
give such number of comparisons for each particular place:
0, 1, …, 7.
All positions have equal possibility, so let’s take the average:

So, the average number of comparisons for a sequential search in the array is 4.5.