Suppose there are 11 items in sorted order in an array. How many searches are required on average, if binary search is employed and all searches are successful in finding the item?

Binary search is an efficient algorithm for finding an item from a sorted list of items. It works by repeatedly dividing in half the portion of the list that could contain the item, until you've narrowed down the possible locations to just one.

Here's how it works:

1. Start with the middle item. If the target item is equal to the middle item, then return the position of the middle item and finish. If not, then continue to step 2.
2. If the target item is less than the middle item, then repeat the process with the left half of the list. Otherwise, repeat the process with the right half of the list.
3. Repeat steps 1 and 2 until you find the target item or until the possible location is empty.

In terms of the number of searches required, binary search has a worst-case and average time complexity of O(log n), where n is the number of items in the array.

So, if there are 11 items in the array, the maximum number of searches required would be log2(11) which is approximately 3.46. Since we can't do a fraction of a search, we round this up to 4 searches.

However, this is the maximum number of searches. On average, the number of searches will be less. The exact average depends on the distribution of the data and the specific item you're searching for. But in general, binary search is a very efficient search method for large sorted arrays.