Exam CTFL_Syll_4.0 Topic 4 Question 99 Discussion

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.
1: ISTQBCertified Tester Foundation Level Syllabus v4.01, Section 2.3.2, page 24-25; ISTQBGlossary v4.
02, page 33.