In:
41-1327: [REDACTED] Look up threshold in Wiktionary, the free dictionary. Threshold may refer to: Science [ edit ] Biology [ edit ] Threshold (reference value) Absolute threshold Absolute threshold of hearing Action potential Aerobic threshold Anaerobic threshold Dark adaptation threshold Epidemic threshold Flicker fusion threshold Masking threshold Odor detection threshold Renal threshold Seizure threshold Sensory threshold Threshold expression Threshold limit value Threshold model Threshold of pain Threshold potential Other science-related [ edit ] Ecological threshold Error threshold (evolution) Extinction threshold Lasing threshold Percolation threshold Polygyny threshold model Threshold cryptosystem Threshold displacement energy Threshold energy Threshold graph Threshold knowledge Threshold model Threshold voltage Thresholding (image processing) Transparency threshold Architecture [ edit ] Threshold (architecture) ,
82-423: A normal distribution or a log-normal distribution , or directly from percentages of interest, as detailed respectively in following sections. When establishing reference ranges from bilateral organs (e.g., vision or hearing), both results from the same individual can be used, although intra-subject correlation must be taken into account. The 95% interval, is often estimated by assuming a normal distribution of
123-547: A reference range or reference interval is the range or the interval of values that is deemed normal for a physiological measurement in healthy persons (for example, the amount of creatinine in the blood , or the partial pressure of oxygen ). It is a basis for comparison for a physician or other health professional to interpret a set of test results for a particular patient. Some important reference ranges in medicine are reference ranges for blood tests and reference ranges for urine tests . The standard definition of
164-405: A 95% prediction interval) 1.96 standard deviations below and above that mean, and subsequently exponentiate using those two logarithms as exponents and using the same base as was used in logarithmizing, with the two resultant values being the lower and upper limit of the 95% prediction interval. The following example of this method is based on the same values of fasting plasma glucose as used in
205-418: A concept in voting systems Poverty thresholds (United States Census Bureau) In government procurement , the expenditure value which determines which rules and procedures are to be applied to a proposed purchase See also [ edit ] All pages with titles containing Threshold Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with
246-419: A log-normal distribution if the difference ratio becomes more than 0.1, meaning that a (lower or upper) limit estimated from an assumed normal distribution would be more than 10% different from the corresponding limit as estimated from a (more accurate) log-normal distribution. As seen in the diagram, a difference ratio of 0.1 is reached for the lower limit at a coefficient of variation of 0.213 (or 21.3%), and for
287-515: A record label created by The Moody Blues Albums [ edit ] Threshold (album) , a 2006 album by HammerFall Thresholds (album) , a 1992 album by Nocturnus Threshold , a 1997 album by Erik Norlander Songs [ edit ] "Threshold", by Pocahaunted , 2010 "Threshold", by Slayer on the album God Hates Us All , 2001 "Threshold", by The Steve Miller Band from Book of Dreams , 1977 "Threshold", by Turnover from Peripheral Vision , 2015 "Threshold," from
328-437: A reference range (usually referred to if not otherwise specified) originates in what is most prevalent in a reference group taken from the general (i.e. total) population. This is the general reference range. However, there are also optimal health ranges (ranges that appear to have the optimal health impact) and ranges for particular conditions or statuses (such as pregnancy reference ranges for hormone levels). Values within
369-415: A reference range by log-normal distribution rather than normal distribution can be regarded as depending on how much difference it would make to not do so, which can be described as the ratio: where: This difference can be put solely in relation to the coefficient of variation , as in the diagram at right, where: where: In practice, it can be regarded as necessary to use the establishment methods of
410-405: A sample has half the value of the mean or median tends to have almost equal probability to occur as the event where a sample has twice the value of the mean or median. Also, only a log-normal distribution can compensate for the inability of almost all biological parameters to be of negative numbers (at least when measured on absolute scales ), with the consequence that there is no definite limit to
451-452: A science-fiction novel by Caitlín R. Kiernan Threshold , a Christian novel by Bill Myers (author) Threshold , a science-fiction novel by Ben Mezrich Threshold Editions , a conservative imprint Media [ edit ] Threshold (1981 film) Threshold , a 2008 film directed by Deepak Rauniyar Threshold (TV series) , an American science fiction drama TV series "Threshold" ( Stargate SG-1 ) , an episode of
SECTION 10
#1732764883340492-433: Is 12 and the standard deviation is 0.42 mmol/L, resulting in: Thus, the lower limit of the reference range can be written as 4.4 (90% CI 4.1–4.7) mmol/L. Likewise, with similar calculations, the upper limit of the reference range can be written as 6.3 (90% CI 6.0–6.6) mmol/L. These confidence intervals reflect random error , but do not compensate for systematic error , which in this case can arise from, for example,
533-405: Is a limit used for binary classification , mainly between normal versus pathological (or probably pathological). Establishment methods for cutoffs include using an upper or a lower limit of a reference range. The standard definition of a reference range for a particular measurement is defined as the interval between which 95% of values of a reference population fall into, in such a way that 2.5% of
574-403: Is based on values of fasting plasma glucose taken from a reference group of 12 subjects: As can be given from, for example, a table of selected values of Student's t-distribution , the 97.5% percentile with (12-1) degrees of freedom corresponds to t 0.975 , 11 = 2.20 {\displaystyle t_{0.975,11}=2.20} Subsequently, the lower and upper limits of
615-444: Is estimated by the sample standard deviation and the population mean is estimated by the sample mean (also called mean or arithmetic mean ). To account for these estimations, the 95% prediction interval (95% PI) is calculated as: where t 0.975 , n − 1 {\displaystyle t_{0.975,n-1}} is the 97.5% quantile of a Student's t-distribution with n −1 degrees of freedom . When
656-645: The Scott Pilgrim vs. the World soundtrack , 2010 "The Threshold", by Connie Smith from Connie Smith , 1965 Other uses [ edit ] Threshold (video game) , a 1981 video game Thresholds , a nonprofit organization serving persons with mental illnesses and substance abuse problems in Illinois Threshold Audio , a manufacturer of high end audio amplifiers Displaced threshold , an aviation term Election threshold ,
697-415: The 1982 Karlovy Vary International Film Festival for his performance. Threshold was filmed on location at the then newly constructed Ottawa General Hospital. Respected cardiac surgeon Dr. Thomas Vrain performs a risky operation to provide a patient with the first artificial heart ever implanted in a human subject. He and his colleague, research scientist Dr. Aldo Gehring, consider the risks and weigh
738-499: The 2.5th and 97.5th percentile of the measurements in the reference group. For example, if the reference group consists of 200 people, and counting from the measurement with lowest value to highest, the lower limit of the reference range would correspond to the 5th measurement and the upper limit would correspond to the 195th measurement. This method can be used even when measurement values do not appear to conform conveniently to any form of normal distribution or other function. However,
779-487: The International Federation of Clinical Chemistry prefer to use the expression reference interval rather than reference range. Regarding the target population, if not otherwise specified, a standard reference range generally denotes the one in healthy individuals, or without any known condition that directly affects the ranges being established. These are likewise established using reference groups from
820-477: The TV series "Threshold" ( Star Trek: Voyager ) , an episode of the TV series Threshold Entertainment , a Hollywood Intellectual Property Management and Production Company Threshold Podcast , a podcast focused on long-form reporting of climate justice topics Music [ edit ] Threshold (band) , a UK progressive metal band Threshold House , a record label created by Coil Threshold Records ,
861-428: The assumption of log-normal distribution is to use the arithmetic mean and standard deviation. This is somewhat more tedious to perform, but may be useful in cases where a study presents only the arithmetic mean and standard deviation, while leaving out the source data. If the original assumption of normal distribution is less appropriate than the log-normal one, then, using the arithmetic mean and standard deviation may be
SECTION 20
#1732764883340902-425: The calculations again by log-normal distribution. Taking the example from previous section, the standard deviation (s.d.) is estimated at 0.42 and the arithmetic mean (m) is estimated at 5.33. Thus the coefficient of variation is 0.079. This is less than both 0.213 and 0.413, and thus both the lower and upper limit of fasting blood glucose can most likely be estimated by assuming normal distribution. More specifically,
943-414: The coefficient of variation of 0.079 corresponds to a difference ratio of 0.01 (1%) for the lower limit and 0.007 (0.7%) for the upper limit. A method to estimate the reference range for a parameter with log-normal distribution is to logarithmize all the measurements with an arbitrary base (for example e ), derive the mean and standard deviation of these logarithms, determine the logarithms located (for
984-495: The healthy population, and are sometimes termed normal ranges or normal values (and sometimes "usual" ranges/values). However, using the term normal may not be appropriate as not everyone outside the interval is abnormal, and people who have a particular condition may still fall within this interval. However, reference ranges may also be established by taking samples from the whole population, with or without diseases and conditions. In some cases, diseased individuals are taken as
1025-676: The log-normal distribution with large standard deviations. In a log-normal distribution, the geometric standard deviations and geometric mean more accurately estimate the 95% prediction interval than their arithmetic counterparts. Reference ranges for substances that are usually within relatively narrow limits (coefficient of variation less than 0.213, as detailed below) such as electrolytes can be estimated by assuming normal distribution, whereas reference ranges for those that vary significantly (coefficient of variation generally over 0.213) such as most hormones are more accurately established by log-normal distribution. The necessity to establish
1066-440: The measured parameter, in which case it can be defined as the interval limited by 1.96 (often rounded up to 2) population standard deviations from either side of the population mean (also called the expected value ). However, in the real world, neither the population mean nor the population standard deviation are known. They both need to be estimated from a sample, whose size can be designated n . The population standard deviation
1107-542: The only available parameters to determine the reference range. By assuming that the expected value can represent the arithmetic mean in this case, the parameters μ log and σ log can be estimated from the arithmetic mean ( m ) and standard deviation ( s.d. ) as: Following the exampled reference group from the previous section: Subsequently, the logarithmized, and later non-logarithmized, lower and upper limit are calculated just as by logarithmized sample values. Reference ranges can also be established directly from
1148-407: The population, establishing reference ranges among those having a disease or condition. Preferably, there should be specific reference ranges for each subgroup of the population that has any factor that affects the measurement, such as, for example, specific ranges for each sex , age group , race or any other general determinant . Methods for establishing reference ranges can be based on assuming
1189-414: The previous section, using e as a base : Subsequently, the still logarithmized lower limit of the reference range is calculated as: and the upper limit of the reference range as: Conversion back to non-logarithmized values are subsequently performed as: Thus, the standard reference range for this example is estimated to be 4.4 to 6.4. An alternative method of establishing a reference range with
1230-512: The reference group not having fasted long enough before blood sampling. As a comparison, actual reference ranges used clinically for fasting plasma glucose are estimated to have a lower limit of approximately 3.8 to 4.0, and an upper limit of approximately 6.0 to 6.1. In reality, biological parameters tend to have a log-normal distribution , rather than the normal distribution or Gaussian distribution. An explanation for this log-normal distribution for biological parameters is: The event where
1271-463: The reference group, and therefore, this method may be optimal where a large reference group easily can be gathered, and the distribution mode of the measurements is uncertain. Threshold (1981 film) Threshold is a 1981 Canadian drama / science fiction film directed by Richard Pearce , and starring Donald Sutherland and Jeff Goldblum . It was nominated for ten Genie Awards in 1983 and won two of them. Sutherland also won best actor at
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1312-419: The reference range ( WRR ) are those within normal limits ( WNL ). The limits are called the upper reference limit (URL) or upper limit of normal (ULN) and the lower reference limit (LRL) or lower limit of normal (LLN). In health care –related publishing, style sheets sometimes prefer the word reference over the word normal to prevent the nontechnical senses of normal from being conflated with
1353-426: The reference range limits as estimated in this way have higher variance, and therefore less reliability, than those estimated by an arithmetic or log-normal distribution (when such is applicable), because the latter ones acquire statistical power from the measurements of the whole reference group rather than just the measurements at the 2.5th and 97.5th percentiles. Still, this variance decreases with increasing size of
1394-458: The sample size is large ( n ≥30) t 0.975 , n − 1 ≃ 2. {\displaystyle t_{0.975,n-1}\simeq 2.} This method is often acceptably accurate if the standard deviation, as compared to the mean, is not very large. A more accurate method is to perform the calculations on logarithmized values, as described in separate section later. The following example of this ( not logarithmized) method
1435-431: The sill of a door Literature [ edit ] Threshold (1990 novel) , a science fiction novel by Chris and Janet Morris Threshold (Sara Douglass novel) , a fantasy novel Threshold (Palmer novel) , a science fiction novel by David R. Palmer Threshold , the first volume of the collected short fiction of Roger Zelazny Threshold (DC Comics) , a comic book published by DC Comics Threshold ,
1476-492: The size of outliers (extreme values) on the high side, but, on the other hand, they can never be less than zero, resulting in a positive skewness . As shown in diagram at right, this phenomenon has relatively small effect if the standard deviation (as compared to the mean) is relatively small, as it makes the log-normal distribution appear similar to a normal distribution. Thus, the normal distribution may be more appropriate to use with small standard deviations for convenience, and
1517-419: The standard reference range are calculated as: Thus, the standard reference range for this example is estimated to be 4.4 to 6.3 mmol/L. The 90% confidence interval of a standard reference range limit as estimated assuming a normal distribution can be calculated by: where SD is the standard deviation, and n is the number of samples. Taking the example from the previous section, the number of samples
1558-409: The statistical sense. Values outside a reference range are not necessarily pathologic, and they are not necessarily abnormal in any sense other than statistically. Nonetheless, they are indicators of probable pathosis. Sometimes the underlying cause is obvious; in other cases, challenging differential diagnosis is required to determine what is wrong and thus how to treat it. A cutoff or threshold
1599-443: The time a value will be less than the lower limit of this interval, and 2.5% of the time it will be larger than the upper limit of this interval, whatever the distribution of these values. Reference ranges that are given by this definition are sometimes referred as standard ranges . Since a range is a defined statistical value ( Range (statistics) ) that describes the interval between the smallest and largest values, many, including
1640-507: The title Threshold . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=Threshold&oldid=1221036109 " Category : Disambiguation pages Hidden categories: Short description is different from Wikidata All article disambiguation pages All disambiguation pages Threshold (reference value) In medicine and health -related fields,
1681-416: The upper limit at a coefficient of variation at 0.413 (41.3%). The lower limit is more affected by increasing coefficient of variation, and its "critical" coefficient of variation of 0.213 corresponds to a ratio of (upper limit)/(lower limit) of 2.43, so as a rule of thumb, if the upper limit is more than 2.4 times the lower limit when estimated by assuming normal distribution, then it should be considered to do