T

Ta

atomic symbol for tantalum

tailing

broadening of the lower portion of a spectral peak on one or both sides, resulting in a non-ideal peak shape

The broadened portion of the peak on either side is called a tail. In a radiation spectrum, the tail may be a low-energy tail or a high-energy tail.

tare

1. (noun) mass of the container in which material is weighed on a balance
2. (transitive verb) to zero a digital balance (setting the zero reference point for the scale of the instrument), as for example when preparing to measure the difference in mass between an empty container and the same container filled with material

tare correction

in a measurement of the mass of material in a container, a correction of the gross result for the mass of the container

Tb

atomic symbol for terbium

Tc

atomic symbol for technetium

t-distribution

Student’s t-distribution

Te

atomic symbol for tellurium

test

A measurement performed on a sample, item, or specimen to determine the value of a particular quantity, such as the massic activity or volumic activity of a specified radionuclide. (A chemical analysis or radiochemical analysis is an example of a test.) The word test may also be used as a modifier for other nouns, as in test portion and test source.

test portion

portion of a test sample taken for analysis, the entire portion being used

test sample

laboratory sample after preliminary preparation steps such as drying and sieving to remove foreign objects

test source

radioactive source prepared from a test portion of a laboratory sample

Th

atomic symbol for thorium

THO

HTO

thoron

traditional name for ²²⁰Rn, an alpha-emitting isotope of radon with a half-life of 55.6(1) s

Ti

atomic symbol for titanium

Tl

atomic symbol for thallium

Tm

atomic symbol for thulium

tolerance chart

graph used to monitor outputs from a process to ensure that observed values remain within specified limits, called tolerance limits

Note: A tolerance chart is somewhat similar to a control chart, but the limits typically are based on judgment or process requirements rather than statistics.

tolerance interval

in statistics, an interval, either one-sided or two-sided, that will contain, with a specified degree of confidence, a specified proportion of a population

tolerance limit

1. in statistics, an endpoint of a tolerance interval
2. in engineering and quality control, a specified lower or upper acceptable limit for some measurable attribute of an item or process

total propagated uncertainty (TPU)

See combined standard uncertainty

traceability

“property of the result of a measurement or the value of a standard whereby it can be related to stated references, usually national or international standards, through an unbroken chain of comparisons all having stated uncertainties” [VIM]

traceability chain

the unbroken chain of comparisons that provide traceability for the result of a measurement or the value of a standard

tracer

foreign substance mixed with a given substance to allow subsequent measurement of the distribution or location of the latter

Note: An isotopic tracer is a unique isotope, either a radioisotope or an enriched uncommon isotope, of the same element as the substance being traced. In radiochemistry a tracer is usually radioactive and is measured by radioassay to determine the chemical yield for one or more analytes.

transient equilibrium

radioactive equilibrium where the half-life of the ancestor radionuclide is longer but not very much longer than the half-lives of the descendants (cf. secular equilibrium)

trapezoidal distribution

probability distribution for which the probability density function has the form

f(x) =

{ (x − (μ − a)) / a2(1 − β2),     if μ − a ≤ x ≤ μ − βa 1 / a(1 + β),     if μ − βa ≤ x ≤ μ + βa ((μ + a) − x) / a2(1 − β2),     if μ + βa ≤ x ≤ μ + a 0,     otherwise.

where μ is the mean of the distribution, a is the half-width, and 0 < β < 1

Note: The graph of this pdf resembles a trapezoid.

triangular distribution

probability distribution for which the probability density function has the form

f(x) =

{ (x − (μ − a)) / a2,     if μ − a ≤ x ≤ μ ((μ + a) − x) / a2,     if μ ≤ x ≤ μ + a 0,     otherwise.

where μ is the mean of the distribution and a is the half-width

Note: The graph of this pdf resembles a triangle.

tritiate

to replace the normal hydrogen atoms of a compound by tritium atoms

tritium

isotope of hydrogen with mass number 3

Tritium is radioactive with a half-life of 12.32(2) a.

tritium unit (TU)

non-SI unit for the ratio of the number of tritium atoms to the total number of hydrogen atoms in a sample or body of water, equal to 10⁻¹⁸ (1 atom of tritium per 10¹⁸ atoms of hydrogen)

tropical year (a)

non-SI unit of time, approximately equal to 365.2422 d — also called mean solar year

true value (of a quantity)

value of a particular quantity that is consistent with its definition [VIM]

Note: One tends to think and say “the true value,” although this definition recognizes the fact that the definition of a particular quantity is almost always somewhat ambiguous, making the phrase “a true value” more correct.

Type A evaluation

“method of evaluation of uncertainty by the statistical analysis of series of observations” [GUM] (cf. Type B evaluation)

Type B evaluation

“method of evaluation of uncertainty by means other than the statistical analysis of series of observations” [GUM]

In other words, a Type B method of evaluation is any method of uncertainty evaluation that is not a Type A evaluation.

type I error

decision error made in a hypothesis test by rejecting the null hypothesis when it is actually true

type II error

decision error made in a hypothesis test by failing to reject the null hypothesis when it is actually false