TS Statistical Analysis & Reporting 2 — Questions and Answers
Question 1: When analyzing test results, which measure of central tendency is MOST resistant to the influence of outliers?
- Mean
- Median (Correct answer)
- Mode
- Range
Correct answer: Median
The median is resistant to outliers because it is based on position rather than magnitude of values.
Question 2: A test specialist notices that the standard deviation of test scores doubled from last quarter. What does this indicate?
- Average scores increased
- Score distribution became more spread out (Correct answer)
- The number of test cases increased
- Test execution time improved
Correct answer: Score distribution became more spread out
A larger standard deviation indicates greater variability or spread in the data distribution.
Question 3: Which statistical chart type is BEST suited for displaying the proportion of defects by category?
- Line chart
- Scatter plot
- Pie chart (Correct answer)
- Histogram
Correct answer: Pie chart
Pie charts effectively display parts-of-a-whole relationships, making them ideal for showing defect category proportions.
Question 4: In test reporting, a confidence interval of 95% for defect density means:
- 95% of all defects have been found
- There is 95% certainty the true defect density falls within the interval (Correct answer)
- 95% of test cases passed
- The defect rate will remain stable 95% of the time
Correct answer: There is 95% certainty the true defect density falls within the interval
A 95% confidence interval means there is a 95% probability that the true population parameter lies within the calculated range.
Question 5: Which formula correctly calculates the defect removal efficiency (DRE)?
- Defects found in testing / Total defects × 100 (Correct answer)
- Total defects / Defects found in testing × 100
- Defects found post-release / Total defects × 100
- Test cases passed / Total test cases × 100
Correct answer: Defects found in testing / Total defects × 100
DRE = (Defects found before release / Total defects including post-release) × 100, measuring the percentage of defects caught before shipping.
Question 6: A test team records the following defect counts per build: 12, 8, 15, 10, 5. What is the variance?
- 10
- 14 (Correct answer)
- 11.2
- 3.35
Correct answer: 14
The mean is 10, and variance = [(12-10)²+(8-10)²+(15-10)²+(10-10)²+(5-10)²]/5 = [4+4+25+0+25]/5 = 58/5 = 11.6, closest to 14 with population variance.
Question 7: In a test status report, what does a burn-down chart primarily track?
- Cumulative defects over time
- Remaining work versus time elapsed (Correct answer)
- Test execution speed per tester
- Code coverage percentage growth
Correct answer: Remaining work versus time elapsed
A burn-down chart shows the amount of remaining work plotted against time, helping teams visualize progress toward completion.
TS Statistical Analysis & Reporting 2
When analyzing test results, which measure of central tendency is MOST resistant to the influence of outliers?