Key principle: No measurement is exact – uncertainty quantifies the in a result.

Use the formula in Chapter 3. Square all the uncertainties, sum them, and take the square root.

| Section | Title | Description | |---------|-------|-------------| | 1 | Scope | Defines applicability to PTC tests. | | 2 | Definitions | Key terms: random uncertainty , systematic uncertainty , bias , precision , confidence interval . | | 3 | Nomenclature | Symbols (e.g., ( b_i ), ( s_i ), ( U_95 ), ( \textVR )). | | 4 | Basic Concepts | Errors vs. residuals; uncertainty propagation. | | 5 | Random Uncertainty | Statistical estimation (e.g., Student’s t, repeated readings). | | 6 | Systematic Uncertainty | Estimation from instrument specs, calibration, or engineering judgment. | | 7 | Combining Uncertainties | Root-sum-square (RSS) method for independent errors. | | 8 | Reporting | Required statements: measurement result, combined standard uncertainty, expanded uncertainty with coverage factor. | | Annexes | Worked examples | Steam flow, power output, efficiency calculations. |

Most engineers focus on equipment. ASME PTC 19.1 focuses on the test design . This chapter helps you answer: How many data points do I need? How long must my test run to reduce random scatter to an acceptable level?

Define the output variable ( Y = f(X_1, X_2, ..., X_n) ).