Preparatory Certificate flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Accuracy

The degree to which a measured value agrees with the accepted reference or true value. Accuracy describes closeness to truth, independent of how tightly repeated readings cluster.

Precision

The degree of agreement among repeated measurements of the same quantity under identical conditions. High precision means tight clustering, but the cluster may still sit far from the true value.

Systematic error

A reproducible deviation that shifts results consistently in one direction, caused by calibration faults, bias, or environmental offsets. It affects accuracy and cannot be reduced by averaging.

Random error

Unpredictable scatter in measurements that varies in magnitude and direction between trials. Averaging repeated observations reduces its influence on the reported mean value.

Significant figures

The digits in a reported value that carry measurement meaning, including one estimated final digit. Multiplication keeps the fewest significant figures among the inputs used.

Control sample

A material of known composition analyzed alongside unknowns to confirm the measurement system is performing within acceptable limits during that specific analytical run.

Sensitivity

The change in instrument response produced by a unit change in the measured quantity. On a linear calibration graph, sensitivity is the slope of the fitted line.

Limit of detection

The smallest quantity of a substance that can be reliably distinguished from a blank at a stated statistical confidence, though not necessarily quantified with acceptable precision.

Tolerance

The total permitted variation in a characteristic, equal to the upper specification limit minus the lower specification limit. It defines acceptable range, not measurement uncertainty.

Calibration

The documented comparison of an instrument's indications against reference standards of known value, establishing the relationship between indicated and reference values across the working range.

Resolution

The smallest change in a quantity that an instrument or display can distinguish. It limits the fineness of reporting but does not by itself establish measurement accuracy.

Repeatability

Closeness of agreement among results obtained with the same method, same operator, same equipment, and same location over a short interval of time.

Measurement uncertainty

A quantified interval characterizing the dispersion of values attributable to a measurement result, reported as a standard uncertainty or an expanded uncertainty with a coverage factor.

Conservation of mass

The principle that mass entering a system equals mass leaving plus any accumulation within it. It provides the balance equation used to check process calculations.

Ohm's law

The relationship stating that voltage equals current multiplied by resistance in an ohmic conductor. It underlies electrical measurement and circuit troubleshooting calculations.

Linear calibration model

The equation y = mx + b relating instrument response to known concentration, where slope m is sensitivity and intercept b is the offset at zero concentration.

Negative feedback

A control arrangement in which part of the output is returned to oppose deviation from the setpoint, reducing error and stabilizing system behavior.

Steady state

A condition in which measured variables remain constant over time even though material or energy flows continuously through the system. It is not the same as equilibrium.

Aliasing

A sampling artifact in which signals above half the sampling rate appear as false lower frequencies. It is prevented by sampling faster than twice the highest frequency present.

Standard operating procedure

A written, approved instruction specifying the steps, materials, conditions, and records required to perform a routine task consistently and reproducibly.

Calibration curve

A plot of instrument response versus known standard concentrations, fitted to estimate unknown concentrations by interpolation within the calibrated range.

Blank determination

A measurement run containing all reagents and procedures except the analyte, used to estimate background signal and detect contamination in the method.

Equivalence point

The theoretical stage in a titration where the reacting amounts are stoichiometrically equal. It is estimated from the titration curve, not read directly from the indicator.

Change one variable

An experimental rule in which only a single factor is altered between trials so that any change in outcome can be attributed to that factor.

Root cause analysis

A structured investigation that identifies the underlying reason a nonconformity or failure occurred, rather than only describing its immediate symptoms.

Rule of ten

A selection guideline requiring instrument resolution to be at most one-tenth of the tolerance being evaluated, so measurement error does not dominate the decision.

Traceability

An unbroken chain of documented calibrations linking an instrument's measurements to national or international reference standards, with stated uncertainties at each link.

Tare function

A balance feature that sets the display to zero with an empty or partially loaded container, so subsequent readings show only the added mass.

Volumetric flask

A laboratory vessel calibrated to contain a precisely known volume at a stated temperature, used to prepare solutions of exact concentration.

Hierarchy of controls

The ranked order of hazard mitigation from most to least effective: elimination, substitution, engineering controls, administrative controls, and personal protective equipment.

Lockout tagout

A procedure that isolates hazardous energy sources with locks and warning tags before maintenance, preventing unexpected energization or release during work.

Safety data sheet

A standardized document listing a substance's hazards, composition, first aid, firefighting measures, handling, exposure controls, and disposal requirements.