Tools › Statistics › Distributions › Distribution Fitting › Example
MIL-HDBK-17-1F Section 8.3.7 Problem 2: normal B-basis value of 20 strengths
| Tool | Distribution Fitting |
| Source | U.S. Department of Defense (2002). Composite Materials Handbook, Volume 1: Polymer Matrix Composites Guidelines for Characterization of Structural Materials. MIL-HDBK-17-1F, 17 June 2002. Section 8.3.7.2, Problem 2; Table 8.5.10. |
| Level | Professional |
Problem
Twenty strength values (106.5, 94.0, 116.1, 98.8, 114.2, 113.8, 98.1, 102.0, 106.0, 98.1, 105.2, 103.3, 103.3, 101.3, 100.4, 94.8, 105.4, 101.5, 95.8, 102.5) are judged normal. Compute the mean and standard deviation, the one-sided tolerance factor k_B for n = 20 and the B-basis value.
Inputs to Enter
- Paste the 20 values of Problem 2 in the data box
- Confidence 95 %, coverage 90 %
Answers
- x̄ = 103.1, s = 6.175
- k_B(20) = 1.927 (Table 8.5.10, noncentral t)
- B-basis = x̄ − k_B s = 91.2
- Table 8.5.10 reproduced for n = 2 … 1000 (20.581 … 1.354) and Table 8.5.11 k_A(20) = 3.295
Notes
Replace the default Problem 1 sample. The handbook's table uses the rounded noncentrality 1.282 √n, which moves k by up to 0.001 against the exact z. Its printed OSL of 0.163 for the RECIPE listing of this problem is not what its own formula gives (0.104); the test records the misprint. Not the default case.