Following a risk-based testing approach you have designed 10 tests to cover a product risk with a high-risk level. You want to estimate, adopting the three-point test estimation technique, the test…

Question

Options

• AThe final estimate is between 22 person hours and 38 person hours
• BThe final estimate is exactly 30 person hours because the technique uses the initial most likely
• CThe final estimate is between 6 person hours and 54 person hours
• DThe final estimate is exactly 30 person hours because the technique uses the arithmetic mean of

• A
  58% (14)
• B
  13% (3)
• C
  4% (1)
• D
  25% (6)

Explanation

Option A is correct because three-point estimation (PERT) produces both a point estimate and a standard deviation that together define a confidence range. Using the weighted formula E = (O + 4M + P) / 6 = (6 + 120 + 54) / 6 = 30 person hours, and the standard deviation SD = (P − O) / 6 = (54 − 6) / 6 = 8 person hours, the final estimate range is E ± SD = 30 ± 8 = [22, 38] person hours.

Why the distractors are wrong:

• B is misleading - while 30 happens to be correct as a point estimate, the technique doesn't simply "use the most likely"; it applies the weighted formula, and the question asks about the full technique output (range included).
• D is wrong because the three-point technique uses a weighted average (4× weight on most likely), not a simple arithmetic mean - it's coincidentally 30 here only because the values are symmetric around 30.
• C is wrong because 6–54 is just the raw input range; the technique refines this into a narrower, more meaningful confidence interval.

Memory tip: Think of three-point estimation as giving you two outputs - a point (the E formula) and a spread (the SD formula). Exam questions often test whether you know that the final answer is a range (E ± SD), not just the single weighted average.

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