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# Topic: Standard deviation

 Standard Deviation and Variance: Common Measures of Variability The standard deviation formula is very simple: it is the square root of the variance. An important attribute of the standard deviation as a measure of spread is that if the mean and standard deviation of a normal distribution are known, it is possible to compute the percentile rank associated with any given score. The standard deviation has proven to be an extremely useful measure of spread in part because it is mathematically tractable. davidmlane.com /hyperstat/A16252.html   (305 words)

 Standard deviation - Wikipedia, the free encyclopedia Standard deviation is the most common measure of statistical dispersion, measuring how spread out the values in a data set are. The standard deviation is defined as the square root of the variance. The term standard deviation was introduced to statistics by Karl Pearson (On the dissection of asymmetrical frequency curves, 1894). en.wikipedia.org /wiki/Standard_deviation   (1534 words)

 Standard error (statistics) - Wikipedia, the free encyclopedia In statistics, the standard error of a measurement, value or quantity is the standard deviation of the process by which it was generated, after adjusting for sample size. In other words the standard error is the standard deviation of the sampling distribution of the sample statistic (such as sample mean, sample proportion or sample correlation). The standard error of a sample from a population is the standard deviation of the sampling distribution and may be estimated by the formula: en.wikipedia.org /wiki/Standard_error_(statistics)   (286 words)

 Standard Deviation The standard deviation value represents the average distance of a set of scores from the mean. A smaller standard deviation represents a data set where scores are very close in value to the mean; a smaller range. Standard deviation is a constant interval from the mean. coe.sdsu.edu /eet/articles/standarddev/start.htm   (271 words)

 Standard deviation Summary In this form the standard deviation is an unbiased estimate of the variance and is sometimes said to be corrected for a loss of a degree of freedom. Standard deviation is the most common measure of statistical dispersion, measuring how spread out the values in a data set are. The standard deviation is defined as the square root of the variance. www.bookrags.com /Standard_deviation   (2153 words)

 Standard deviation   (Site not responding. Last check: 2007-10-26) We distinguish between the standard deviation σ sigma) of a whole population or of a random variable and the standard deviation s of a sample. The term standard deviation was introduced to by Karl Pearson (On the dissection of asymmetrical frequency curves 1894). Simply put the standard deviation tells us far a typical member of a sample population is from the mean value of that sample or population. www.freeglossary.com /Standard_deviation   (829 words)

 Standard Deviation   (Site not responding. Last check: 2007-10-26) The standard deviation is one of several indices of variability that statisticians use to characterize the dispersion among the measures in a given population. To calculate the standard deviation of a population it is first necessary to calculate that population's variance. Numerically, the standard deviation is the square root of the variance. www.sysurvey.com /tips/statistics/standardd.htm   (78 words)

 Standard Deviation   (Site not responding. Last check: 2007-10-26) The standard deviation is the square root of the average squared deviation from the mean. The standard deviation of the Year 2 Internal Medicine scores was 6.9; therefore, we can conclude that 68% of the class fell within plus or minus 6.9 points of the mean. The deviation method is considered first, since it closely parallels the concept of standard deviation. research.med.umkc.edu /tlwbiostats/variability.html   (412 words)

 Standard Deviation (Volatility)   (Site not responding. Last check: 2007-10-26) Standard deviation is a statistical term that provides a good indication of volatility. There is a different kind of Standard Deviation calculation that is used when you are taking a statistical sample of a population, but that version is not used in technical analysis since all of the data points are known. Because Standard Deviation is used to determine the spread between upper and lower Bollinger Bands, the Bollinger Band Width indicator can be used as a substitute for the Standard Deviation indicator. www.stockcharts.com /education/IndicatorAnalysis/indic_standardDev.html   (550 words)

 Standard Deviation Standard deviation is the square roots of the sum of the squared differences between each score and the mean average of all scores. We need some level of understanding of what standard deviation represents, and the issue of the standard deviation of a population versus calculating an estimate of the population parameter when using samples drawn for a population. The standard deviation statistic is a number that marks a distance on the measurement scale. www.documentingexcellence.com /stat_tool/SD.htm   (400 words)

 Standard deviation The standard deviation is defined as the average amount by which scores in a distribution differ from the mean, ignoring the sign of the difference. To calculate the standard deviation for a population, N is used in the denominator instead of N-1. Using the N-1 version of the formula, we still define the standard deviation as the average amount by which scores in a distribution differ from the mean, ignoring the sign of the difference, even though this isnÃ•t a true average using this formula. www.une.edu.au /WebStat/unit_materials/c4_descriptive_statistics/standard_deviation.htm   (518 words)

 Standard Deviation   (Site not responding. Last check: 2007-10-26) The standard deviation is the square root of the average squared deviation from the mean. The standard deviation of the Year 2 Internal Medicine scores was 6.9; therefore, we can conclude that 68% of the class fell within plus or minus 6.9 points of the mean. The deviation method is considered first, since it closely parallels the concept of standard deviation. www.med.umkc.edu /tlwbiostats/variability.html#deviation   (412 words)

 1.3.3.28. Standard Deviation Plot   (Site not responding. Last check: 2007-10-26) Standard deviation plots are used to see if the standard deviation varies between different groups of the data. Although the standard deviation is the most commonly used measure of scale, the same concept applies to other measures of scale. For example, instead of plotting the standard deviation of each group, the median absolute deviation or the average absolute deviation might be plotted instead. www.itl.nist.gov /div898/handbook/eda/section3/sdplot.htm   (380 words)

 Learning Resources: Statistics: Power from Data! Variance and standard deviation Standard deviation is the measure of spread most commonly used in statistical practice when the mean is used to calculate central tendency. Standard deviation is also influenced by outliers; one value could contribute largely to the results of the standard deviation. Standard deviation might be difficult to interpret in terms of how big it has to be in order to consider the data widely spread. www.statcan.ca /english/edu/power/ch12/variance.htm   (1369 words)

 GFX Forex Training Standard deviation is a statistical term that provides a good indication of volatility. The calculation for the standard deviation is based on the number of periods chosen. The standard deviation for the 20 periods is 6.787. www.forex.ch /training/sd.htm   (215 words)

 Standard Deviation: Formula, Algorithm, Software Standard deviation is a fundamental element of randomness. The standard deviation is viewed as: - a probability parameter of binomial events (compared to the expected value) = standard deviation proper; - a statistical parameter of a numerical series (compared to the mean); i.e. The statistical standard deviation formula is calculated as the square root of the variance; the variance is the average of the differences from the mean of the series. www.saliu.com /deviation.html   (2803 words)

 Concept The standard deviation is one number that is used to express how far (on average) the data points are from the mean value of the data set. The sample standard deviation is the square root of the sum of the squared differences around the arithmetic mean divided by the sample size minus 1. The population standard deviation is the square root of the sum of the squared differences around the arithmetic mean divided by the size of the population. mtsu32.mtsu.edu:11308 /regression/level1/meanstdev/stdevconceptdefinition.htm   (168 words)

 Standard Deviation   (Site not responding. Last check: 2007-10-26) The standard deviation is a statistic that tells you how tightly all the various values are clustered around the mean in a set of data. The red area on the above graph is one standard deviation away from the mean in either direction on the horizontal axis and accounts for about 68% of the values in the set of data. Two standard deviations away from the mean is shown by the red and green areas and accounts for roughly 95 percent of the values. www.stoller-eser.com /Deviation.htm   (149 words)

 Standard Deviation at Trade10.com- The science of trading market momentum for stocks, options, futures and bonds. Standard deviation is the measure of tightness of a probability distribution. Standard deviation is calculated by first calculating the mean of a group of data points. As a measure of volatility, standard deviation have been used in the construction of Bollinger bands as an upper and lower band that are a certain standard deviation level away from a central moving average. www.trade10.com /standard_deviati.htm   (1224 words)

 Standard Deviation and Variance The Standard Deviation (σ) is a measure of how spread out numbers are. And the good thing about the Standard Deviation is that it is useful. So, using the Standard Deviation we have a "standard" way of knowing what is normal, and what is extra large or extra small. www.mathsisfun.com /probability/standard-deviation.html   (288 words)

 Standard Deviation Calculation According to Drummond and Jones (2006), a standard deviation "is the numerical value that describes the spread of scores away from the mean and is expressed in the same units as the original scores. A standard deviation is calculated by subtracting the mean of a distribution from the value of each individual variable in the distribution, squaring each resulting difference, summing these squared differences, then dividing this sum by the number of variables, and finally taking the square root of this quotient. When we have a small sample (typically 20 or fewer variables) it is generally recommended that we substitute n-1 for n so that the standard deviation is not underestimated. faculty.tamu-commerce.edu /crrobinson/517/sdcalc.htm   (419 words)

 Standard Deviation The calculation for the standard deviation is based on the number of periods chosen. Divide the sum of the squared deviations by 20 (921.28/20 = 46.06). The standard deviation for the 20 periods is 6.787. www.forex-training.com /sd.htm   (215 words)

 Standard Deviation - MC Magazine May/June 2004 - Concrete Publications - NPCA A standard deviation measures the variance of a set of numbers from the average. Standard deviations can provide the precast concrete producer with a means of evaluating mix designs for consistency, and this article explains how. Standard deviations are a broad measure of quality in your production operation and will provide a clear sign if changes are necessary. www.precast.org /publications/mc/2004_mayjun/standard_deviation.htm   (1603 words)

 Standard Deviation Standard deviation is a statistical measure of the scattering of a set of data. is the standard deviation of the data, and n is the number of data values) of the mean value, and about an 95% probability that the "true value" will lie within twice this distance from the mean value. For now, notice that most (but not all) of the data falls within one standard deviation of the mean value, and just about all of the data falls within two standard deviations of the mean. www.batesville.k12.in.us /physics/APPhyNet/Measurement/standard_deviation.htm   (686 words)

 eBMJ -- Statistics at Square One: 2. Mean and standard deviation The standard deviation is a summary measure of the differences of each observation from the mean. This procedure illustrates the structure of the standard deviation, in particular that the two extreme values 0.1 and 3.2 contribute most to the sum of the differences squared. Obtain the mean and standard deviation of the data in and an approximate 95% range. bmj.bmjjournals.com /collections/statsbk/2.shtml   (2546 words)

 Standard Deviation (Volatility) - StockCharts.com   (Site not responding. Last check: 2007-10-26) The standard deviation is then equal to the square root of that number. There is a different kind of Standard Deviation calculation that is used when you are taking a statistical sample of a population, but that version is not used in technical analysis since all of the data points are known. Because Standard Deviation is used to determine the spread between upper and lower Bollinger Bands, the Bollinger Band Width indicator can be used as a substitute for the Standard Deviation indicator. stockcharts.com /education/IndicatorAnalysis/indic_standardDev.html   (528 words)

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