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 only help to identify one of them? These two-variable problems, like intermittent phenomena, can create baffling, frustrating search and equipment-troubleshooting puzzles. Somehow one needs to separate the two (possibly unknown) factors, as in the one-dimensional search procedure above.

When the search succeeds, minimize recurrence problems:
 * prevent another loss of the object, or
 * make the solution a permanent one rather than a temporary fix-up, or
 * make a permanent record of the solution or successful search technique, and assure that this record does not have to be searched for. For equipment problems, paste a label on the equipment describing the symptom and solution.

Each of the search tactics above can be invaluable on occasion. For particularly intractable search or exploration problems, it can be worthwhile to scan the techniques above, considering the appropriateness of each. Many search problems, however, can be solved by a relatively simple series of steps:
 * 1) describe the problem thoroughly;
 * 2) list the differences between ‘signal’ and ‘noise’;
 * 3) evaluate the potential benefit of each difference for the current problem;
 * 4) consider employing a discrimination of more than one difference, either in series (first cut then final discrimination) or in parallel (simultaneous).

Problem: Find a Needle in a Haystack.
Hint #1: First, define the problem more thoroughly. Ask, “Why do you need to find it?” This is not just a smart-ass question. It is a recognition that there may be many ways to solve a problem, and individual requirements determine the optimum approach. Are you after the needle or a needleless haystack? Which is dispensable: the needle, haystack, or both? Is this a one-time or repetitive problem? Are you certain that the haystack contains only one needle? How critical is it that no mistakes are made?

What is the best way to find a needle in a haystack, given each of the following scenarios?
 * Feeding this hay to your thoroughbred horse could give it a punctured stomach.
 * The only possible supplier of hay for your thoroughbred-horse stable provides hay that sometimes is unavoidably contaminated with needles.
 * You are doing some sewing, and you just lost your needle in the haystack.
 * A valuable golden needle is lost in the haystack.

Hint #2: Before deciding on a technique, list the characteristics in which the search object can be distinguished from background: