estimation technique applied to this problem is true?

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 effort required to reduce the risk level to zero by executing those 10 tests.

You made the following three initial estimates:

• most optimistic = 6 person hours

• most likely = 30 person hours

• most pessimistic = 54 person hours

Based only on the given information, which of the following answers about the three-point test

estimation technique applied to this problem is true?

A. The final estimate is between 22 person hours and 38 person hours

B. The final estimate is exactly 30 person hours because the technique uses the initial most likely estimate as the final estimate

C. The final estimate is between 6 person hours and 54 person hours

D. The final estimate is exactly 30 person hours because the technique uses the arithmetic mean of the three initial estimates as the final estimate

View Answer

Answer: A

Explanation:

The three-point test estimation technique is a method of estimating the test effort based on three initial estimates: the most optimistic, the most likely, and the most pessimistic. The technique uses a weighted average of these three estimates to calculate the final estimate, which is also known as the expected value.

The formula for the expected value is:

Expected value = (most optimistic + 4 * most likely + most pessimistic) / 6

Using the given values, the expected value is:

Expected value = (6 + 4 * 30 + 54) / 6 Expected value = 30 person hours

However, the expected value is not the only factor to consider when estimating the test effort. The technique also calculates the standard deviation, which is a measure of the variability or uncertainty of the estimates. The formula for the standard deviation is: Standard deviation = (most pessimistic – most optimistic) / 6

Using the given values, the standard deviation is:

Standard deviation = (54 – 6) / 6 Standard deviation = 8 person hours

The standard deviation can be used to determine a range of possible values for the test effort, based on a certain level of confidence. For example, using a 68% confidence level, the range is: Expected value ± standard deviation

Using the calculated values, the range is:

30 ± 8 person hours

Therefore, the final estimate is between 22 person hours and 38 person hours, which is option A.

Reference: ISTQB® Certified Tester Foundation Level Syllabus v4.01, Section 2.3.2, page 24-25; ISTQB® Glossary v4.02, page 33.