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Q: Why standard deviation is better measure of variance?

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Because it is in same units as the original data. For example, if you have a sample of lengths, all in centimetres, the sample variance will be in units of centrimetres2 which might be more difficult to interpret but the sample standard deviation with be in units of centimetres, which would be relatively easy to intepret with reference to the data.

There may or may not be a benefit: it depends on the underlying distributions. Using the standard normal distribution, whatever the circumstances is naive and irresponsible. Also, it depends on what parameter you are testing for. For comparing whether or not two distributions are the same, tests such as the Kolmogorov-Smirnov test or the Chi-Square goodness of fit test are often better. For testing the equality of variance, an F-test may be better.

Variance is basically the raw material of statistics. If you don't have variance (differences in scores) you don't have much to work with or for that matter you don't have much to talk or think about. Consider a test where everyone gets the same score. What does that tell you? You might have some measurement problem, wherein the test is so easy everyone aces it. Still it might be so hard that everyone gets a zero. Now consider two tests. On each everyone gets the same score. That is on test one everyone gets a 15 and on the second test everyone gets a 10. That isn't telling you much is it? Now these are extreme cases, but in general, more variance is better and less variance isn't so good.

The quadratic mean is a measure of the spread of values about their arithmetic mean. By definition, the arithmetic mean of the differences will be zero and so adds no information. Another measure is required and that is the quadratic mean.

Small physical size when tape is rolled up - most are 5 meters or more long, 5 meters of cord is a big pile. A tape measure is stiff, a cord will stretch so accuracy is better, you can hook the end of a tape measure over it, walk all the way to the end to measure, a cord you would have to fit it (nail/tape) at one end first, so ease of use.

Related questions

Better for what? Standard deviation is used for some calculatoins, variance for others.

Because it is in same units as the original data. For example, if you have a sample of lengths, all in centimetres, the sample variance will be in units of centrimetres2 which might be more difficult to interpret but the sample standard deviation with be in units of centimetres, which would be relatively easy to intepret with reference to the data.

The standard deviation is better since it takes account of all the information in the data set. However, the range is quick and easy to compute.

The Standard deviation is an absolute measure of risk while the coefficent of variation is a relative measure. The coefficent is more useful when using it in terms of more than one investment. The reason being that they have different returns on average which means the standard deviation may understate the actual risk or overstate depending.

When you don't have the population standard deviation, but do have the sample standard deviation. The Z score will be better to do as long as it is possible to do it.

true

score of 92

What is mean deviation and why is quartile deviation better than mean deviation?

deviation 15 is better

You most certainly can. The standard deviation, however, has better statistical properties.

to calculate the standard deviation you must put each number in order from the least to the gr east then you must find your mean after you find your mean you must subtract your mean from each of the data set numbers once you finishsubtracting the data set numbers you add them up and divide by the amount of numbers there are and you have found the standard deviation.

100 is the average IQ whatever your age. A variance of plus or minus 10 points is considered within expected deviation. 100 is the average IQ, but it does vary on age. An IQ of a 113 for an adult is above average, so this should be slightly better for someone younger. 140 (Standard deviation of 20) or above is considered eligible for MENSA.

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