
	Where results make sense

Topic: Random error

	Measurement Error
		Random error is caused by any factors that randomly affect measurement of the variable across the sample.
		The important property of random error is that it adds variability to the data but does not affect average performance for the group.
		Unlike random error, systematic errors tend to be consistently either positive or negative -- because of this, systematic error is sometimes considered to be bias in measurement.
	www.socialresearchmethods.net /kb/measerr.htm (600 words)

	Experimental Error
		Systematic error is an error inherent in the experimental set up which causes the results to be skewed in the same direction every time, i.e., always too large or always too small.
		One example of systematic error would be trying to measure the fall time of a ping pong ball to determine the acceleration due to gravity.
		Random errors will cause a series of measurements to be sometimes too large and sometimes too small.
	www2.volstate.edu /tfarris/PHYS2110-2120/experimental_error.htm (1203 words)

	Error Propagation...
		Random errors, on the other hand, cannot be described by a predetermined mathematical model; rather, they obey the laws of probability.
		Error in this computed value is a function of the errors in the measured values and is evaluated by error propagation analysis.
		Notice that the error magnitudes tend to increase the further the point is from fixed control and that the increase is non-linear.
	www.engr.csufresno.edu /~4sight/error.html (1677 words)

	Random Genetic Drift
		One aspect of genetic drift is the random nature of transmitting alleles from one generation to the next given that only a fraction of all possible zygotes become mature adults.
		In the second generation, there is another sampling error based on the new gene frequency, so the frequency of "a" may go from 0.0505 to 0.501 or back to 0.498.
		The final result of this random change in allele frequency is that the population eventually drifts to p=1 or p=0.
	www.talkorigins.org /faqs/genetic-drift.html (1812 words)

	Errors and residuals in statistics - Wikipedia, the free encyclopedia
		Error is a misnomer; an error is the amount by which an observation differs from its expected value; the latter being based on the whole population from which the statistical unit was chosen randomly.
		The nomenclature arose from random measurement errors in astronomy.
		The sum of the errors need not be zero; the errors are independent random variables if the individuals are chosen from the population independently.
	en.wikipedia.org /wiki/Errors_and_residuals_in_statistics (544 words)

	CHP - Error (Site not responding. Last check: 2007-11-07)
		Random error is the irreproducibility in making replicate measurements and affects the precision of a result.
		Systematic errors are errors that produce a result that differs from the true value by a fixed amount.
		An example of a method error would be partial loss of a volatile analyte during the ashing step in graphite furnace atomic absorption (AA) spectroscopy.
	www.chem.vt.edu /chem-ed/data/error.html (162 words)

	PHYS 2211L - Propagation of Error Supplement
		Since each error term in equation 2 is as likely to be too high or too low (positive or negative), simple summation of the terms would overestimate the actual total error.
		A systematic error will affect all measurements of a quantity in the same way; all will be either too high or too low when compared to the true or accepted value of the quantity.
		If random error dominates, the magnitudes of the individual terms within the square root of equation 3 should be examined to determine which is the largest contributor to the uncertainty in the measured quantity.
	a-s.clayton.edu /campbell/physics/phys2211/Supplements/err2211.htm (969 words)

	ERROR ANALYSIS
		Possible sources of systematic error must be considered in all of the stages of the experiment, from design to the data analysis.
		Random Error is the error from the true value which occurs in any physical measurement.
		In keeping with the assumption of random errors, all variables used in the error equations MUST be independent variables.
	class.phys.psu.edu /p559/experiments/html/error.html (1323 words)

	Error Analysis
		Systematic errors are errors which tend to shift all measurements in a systematic way so their mean value is displaced.
		Random errors are errors which fluctuate from one measurement to the next.
		The first error quoted is usually the random error, and the second is called the systematic error.
	teacher.nsrl.rochester.edu /phy_labs/AppendixB/AppendixB.html (3087 words)

	[No title]
		Random and Fixed Variables A “fixed variable” is one that is assumed to be measured without error.
		Random and Fixed Effects The terms “random” and “fixed” are used in the context of ANOVA and regression models, and refer to a certain type of statistical model.
		Random effects models are sometimes referred to as “Model II” or “variance component models.” Analyses using both fixed and random effects are called “mixed models.” Fixed and Random Coefficients in Multilevel Regression The random vs. fixed distinction for variables and effects is important in multilevel regression.
	www.upa.pdx.edu /IOA/newsom/mlrclass/ho_randfixd.doc (935 words)

	Minimizing Random Error
		In contrast to systematic error, random error can usually be estimated and minimized through statistical analysis of repeated measurements.
		In other words, if we repeated our 25-student sampling procedure 20 times, we would expect our error limits to include the true mean 19 times out of the 20 samples, and miss it completely in one case out of 20.
		refers to the error in measuring the average; whether this is useful depends on the situation.
	instruct1.cit.cornell.edu /Courses/virtual_lab/LabZero/Minimizing_Random_Error.shtml (443 words)

	Observational error - Wikipedia, the free encyclopedia
		When either randomness or uncertainty modeled by probability theory is attributed to such errors, they are "errors" in the sense in which that term is used in statistics; see errors and residuals in statistics.
		The random error (or random variation) is due to factors which we cannot (or do not) control.
		Random error often occurs when instruments are pushed to their limits.
	en.wikipedia.org /wiki/Observational_error (293 words)

	magnitude of random appraisal error in commercial real estate valuation, The Journal of Real Estate Research, The - ...
		Random appraisal error appears constant across both time and the institutional-grade investment universe, except during infrequent periods of real estate market gridlock.
		It follows that any description of the effect of appraisal error on investment statistics should be more complicated than suggested by previous studies, since random and nonrandom appraisal error components affect sample means, variances and correlations in very different ways.
		The magnitude of random appraisal error can be determined empirically if an appraisal database for institutional-grade commercial real estate can be located that includes at least two simultaneous independent appraisals whenever an appraisal valuation is updated.
	www.findarticles.com /p/articles/mi_qa3750/is_199901/ai_n8838736 (693 words)

	Error Propagation
		Error propagation is a way of combining two or more random errors together to get a third.
		Error propagation can also be used to combine several independent sources of random error on the same measurement.
		For example, you could have a known random error associated with your equipment and find that thing you're studying is physically fluctuating to some degree.
	instructor.physics.lsa.umich.edu /ip-labs/tutorials/errors/prop.html (987 words)

	Geol 333 - Error Propagation Lab Exercise
		The error propagation shown here is simpler and more direct, and only requires an estimate of error for each variable in an equation, instead of a measurement population.
		If each addend can be assumed to have random Gaussian error, and the error is expressed as its standard deviation S, then we are really combining the populations to create a population of sums, which will have its own standard deviation.
		Formally, errors should be estimated by passing the whole population of measurements through the entire computation, and then observing the statistics of the final result (histogram, mean, standard deviation, median).
	www.seismo.unr.edu /ftp/pub/louie/class/333/error.html (1482 words)

	Westgard QC Lesson: Critical-Error Graphs
		For random error, a 2.42-fold increase in the CV (i.e., an increase to 4.8%) needs to be detected by the QC procedure.
		Error detection varies from 0.43 to 0.73, which is somewhat lower than observed for the critical systematic error, illustrating that it is generally more difficult to detect the critical changes in random error.
		With a critical-error graph, a quality planing model is used to determine the error condition of interest on the x-axis, then the power curve interpolated to determine the y-value or probability of detecting that error condition.
	www.westgard.com /lesson5.htm (1212 words)

	ANALYTICAL CHEMISTRY - RANDOM ERROR (Site not responding. Last check: 2007-11-07)
		Are related to the small, random errors in an experiment that combine to give an overall error.
		The four errors follow a Gaussian (normal error curve) distribution, randomly combining in all possible combinations.
		Because indeterminate error generally follows a normal distribution, calculations can be based upon characteristics of the normal distribution curve.
	www.sbuniv.edu /~ggray/CHE3345/chp6.html (811 words)

	Uncertainties and Error Propagation
		Systematic error is the result of a mis-calibrated device, or a measuring technique which always makes the measured value larger (or smaller) than the "true" value.
		The instrument limit of error, ILE for short, is the precision to which a measuring device can be read, and is always equal to or smaller than the least count.
		The standard error in the mean in the simplest case is defined as the standard deviation divided by the square root of the number of measurements.
	www.rit.edu /~uphysics/uncertainties/Uncertaintiespart1.html (2751 words)

	General Chemistry Online: Glossary:
		Random errors are errors that affect the precision of a set of measurements.
		Random error scatters measurements above and below the mean, with small random errors being more likely than large ones.
		For example, if three replicate weights for an object are 2.00 g, 2.05 g, and 1.95 g, the absolute error can be expressed as ± 0.05 g and the relative error is ± 0.05 g / 2.00 g = 0.025 = 2.5%.
	antoine.frostburg.edu /chem/senese/101/glossary/r.shtml (838 words)

	Error Analysis
		Often the sources of random errors cannot be identified, and random errors cannot be predicted.
		The errors in measurement of y are assumed to follow a Gaussian or normal distribution, the familiar "bell-shaped curve".
		Error does not mean discrepancy between your result and the "right" result found in some textbook.
	www.cas.muohio.edu /~marcumsd/p293/lab0/lab0.htm (2549 words)

	The Myth of the Random Error (Site not responding. Last check: 2007-11-07)
		So all in all we have a systematic error that varies roughly between +11 µm and -9 µm, a random error of 7.44 µm and two inexplicable events that do not fit the model.
		Adding 3 of the random error (one side of the distribution) to the worst case systematic error to give us a 99.97% worst case uncertainty (disregarding the fliers and assuming that the rest of the observations represent a normal distribution), we get an uncertainty value of 14.72 µm.
		Fortunately, the error we commit when assuming the wrong distribution, generally changes the effect of the contributor no more than 15 - 20 % and it is possible to always err on the safe side, by always choosing the most conservative of the two considered distributions, when in doubt.
	www.hn-metrology.com /randmyth.htm (3499 words)

	Simulating data with random error
		The function RAN3 (defined in Numerical Recipes) generates uniformly distributed random numbers and the function GASDEV transforms them to a Gaussian distribution with a mean of zero and a standard deviation you enter.
		If you choose relative error, Prism first calculates a random number from a Gaussian distribution with a mean of zero and with a SD equal to the percent error you enter.
		To compute a random number from a t distribution with df degrees of freedom, Prism generates df+1 different random numbers drawn from a Gaussian distribution.
	www.graphpad.com /help/Prism5/stat_simulating_data_with_random_error.htm (843 words)

	PHYSICS - Error Analysis (Site not responding. Last check: 2007-11-07)
		Typically, the error of such a measurement is equal to one half of the smallest subdivision given on the measuring device.
		Systematic errors result when characteristics of the system we are examining, or the instruments we use are different from what we assume them to be.
		In light of the above discussion of error analysis, discussions of significant figures (which you should have had in previous courses) can be seen to simply imply that an experimenter should quote digits which are appropriate to the uncertainty in his result.
	felix.physics.sunysb.edu /~allen/252/PHY_error_analysis.html (1890 words)

	OpenSSL: Support, Frequently Asked Questions
		If this error occurs and is not discussed in the documentation of the application you are using, please contact the author of that application; it is likely that it never worked correctly.
		Sometimes the openssl command line utility does not abort with a "PRNG not seeded" error message, but complains that it is "unable to write 'random state'".
		If you can't do this (for example it is a pre-compiled binary) you can use the errstr utility on the error code itself (the hex digits after the second colon).
	www.openssl.org /support/faq.html (5878 words)

	4.2.1.6. The explanatory variables are observed without error.
		In addition, the errors associated with each explanatory variable must be independent of the errors associated with all of the other explanatory variables, and also independent of the observed values of each explanatory variable.
		The Berkson model would apply, though, as long as the errors in measuring the temperature randomly differed from one another each time an observed value of 450 degrees was used and the mean of the true temperatures over many repeated runs at an oven setting of 450 degrees really was 450 degrees.
		Then, as long as the model was also a straight line relating the concentration to the observed values of temperature, the errors in the measurement of temperature would not bias the estimates of the parameters.
	www.itl.nist.gov /div898/handbook/pmd/section2/pmd216.htm (974 words)

	kirupaForum - Random error ? (Site not responding. Last check: 2007-11-07)
		But the weird thing is that (as already said) this error occurs randomly.
		This code creates a grid, and fades a random box out, and when that box reaches alpha 90 is fades another random box out.
		The whole doesn't work/work is totally random, so there has to be something wrong in the code.
	www.kirupa.com /forum/printthread.php?t=32275 (718 words)

	block-random.php error \| Gallery (Site not responding. Last check: 2007-11-07)
		If you are running into this limit it is likley your script has a memory leak in it, alternatively if you are loading large amounts of binary data into ram consider using temporary disk space storage instead of loading it in it's entirity into ram.
		Is there no way to display a random imag eother than this....
		At the moment, there is no solution other than reachitecting the entire random block design.
	gallery.menalto.com /node/24071 (762 words)

	error vs random error (Site not responding. Last check: 2007-11-07)
		Hi, I had this argument with my boss (who is not exactly a physicist) as too whether writing f = a +/- b implies that b includes all estimated errors or just the random error.
		I was tought that "b" should include both random and systematic errors b = sqrt(b_systematic^2 + b_random^2).
		My boss also says that it is the common practice in all fields of science to only include the random error in "b", which is estimated by repeating the same experiment several times.
	www.lns.cornell.edu /spr/2001-04/msg0032585.html (175 words)

	Error with random image block \| Gallery
		Having similar errors on a recently upgraded 1.4.1 (from 1.3.something) gallery with "latest" block recently (minutes ago) d/l'd from www.holzapfel-online.de
		the only quirk- prior to upgrade, I hade a center block with two random blocks (which were called from the same inactive block) worked fine, each instance pulled a separate random image, life was grand.
		(the new block has you pick which album the random image is selected from...
	gallery.menalto.com /node/12824 (408 words)

	Hot Music Radio Links Directory Free Downloads Mp3, Quicktime and WMA's
		The random file, as specified in the $random_file perl variable was unopenable.
		The file was not found on your file system.
		This means that it has either not been created or the path you have specified in $trrandom_file is incorrect.
	www.hotmusicradio.com (406 words)

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