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The longevity of people living in a certain locality has a standard deviation of 14 years what is the mean longevity if 30 percent of the people live longer than 75 years?
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Why use standard deviation In what situations is it special?
I will restate your question as "Why are the mean and standard deviation of a sample so frequently calculated?". The standard deviation is a measure of the dispersion of the data. It certainly is not the only measure, as the range of a dataset is also a measure of dispersion and is more easily calculated. Similarly, some prefer a plot of the quartiles of the data, again to show data dispersal.t Standard deviation and the mean are needed when we want to infer certain information about the population such as confidence limits from a sample. These statistics are also used in establishing the size of the sample we need to take to improve our estimates of the population. Finally, these statistics enable us to test hypothesis with a certain degree of certainty based on our data. All this stems from the concept that there is a theoretical sampling distribution for the statistics we calculate, such as a proportion, mean or standard deviation. In general, the mean or proportion has either a normal or t distribution. Finally, the measures of dispersion will only be valid, be it range, quantiles or standard deviation, require observations which are independent of each other. This is the basis of random sampling.
IQ scores are normally distributed with a mean of 100 and a standard deviation of 15 If a certain statistician has an IQ of 140 what percent of the population has an IQ less than she does?
99.6% for
The average amount customers at a certain grocery store spend yearly is 636.55 Assume the variable is normally distributed If the standard deviation is 89.46 find the probability that a randomly?
.820=82.0%
What is the of z-score -1.0?
A z score is a value that is used to indicate the distance of a certain number from the mean of a normally distributed data set. A z score of -1.0 means that the number is one standard deviation below the mean. A z score of +1.0 means that the number is one standard deviation above the mean. Z scores normally range from -4.0 to +4.0. Hope this helps! =)
What is the difference standard error of mean and sampling error?
The standard error of the mean and sampling error are two similar but still very different things. In order to find some statistical information about a group that is extremely large, you are often only able to look into a small group called a sample. In order to gain some insight into the reliability of your sample, you have to look at its standard deviation. Standard deviation in general tells you spread out or variable your data is. If you have a low standard deviation, that means your data is very close together with little variability. The standard deviation of the mean is calculated by dividing the standard deviation of the sample by the square root of the number of things in the sample. What this essentially tells you is how certain are that your sample accurately describes the entire group. A low standard error of the mean implies a very high accuracy. While the standard error of the mean just gives a sense for how far you are away from a true value, the sampling error gives you the exact value of the error by subtracting the value calculated for the sample from the value for the entire group. However, since it is often hard to find a value for an entire large group, this exact calculation is often impossible, while the standard error of the mean can always be found.
How is standard deviation useful?
It's used in determining how far from the standard (average) a certain item or data point happen to be. (Ie, one standard deviation; two standard deviations, etc.)
What is the significance of standard deviation?
To see how wide spread the results are. If the average (mean) grade for a certain test is 60 percent and the standard deviation is 30, then about half of the students are not studying. But if the mean is 60 and the standard deviation is 5 then the teacher is doing something wrong.
How standard deviation formula can be used in in cement industry?
Usually, industrial use of standard deviation is involved in quality control and testing. A product such as cement, is produced in batches, and I assume, requires periodic testing to ensure consistent properties. The sample test variations can be evaluated using standard deviation. If the standard deviation is high, it is likely that inferior product could be shipped. Probability analysis can determine the chance that product below certain standards would be shipped.
Do you have to do math for psychology?
Yes, to a certain extent. To record data in psychology, such as taking a survey, you record the mean, median, mode, and standard deviation of that group.
Why use standard deviation In what situations is it special?
I will restate your question as "Why are the mean and standard deviation of a sample so frequently calculated?". The standard deviation is a measure of the dispersion of the data. It certainly is not the only measure, as the range of a dataset is also a measure of dispersion and is more easily calculated. Similarly, some prefer a plot of the quartiles of the data, again to show data dispersal.t Standard deviation and the mean are needed when we want to infer certain information about the population such as confidence limits from a sample. These statistics are also used in establishing the size of the sample we need to take to improve our estimates of the population. Finally, these statistics enable us to test hypothesis with a certain degree of certainty based on our data. All this stems from the concept that there is a theoretical sampling distribution for the statistics we calculate, such as a proportion, mean or standard deviation. In general, the mean or proportion has either a normal or t distribution. Finally, the measures of dispersion will only be valid, be it range, quantiles or standard deviation, require observations which are independent of each other. This is the basis of random sampling.
What are uses of standard deviation in business?
Using standard deviations someone can tell how likely a person is to do something, or how often the majority do, e.g. how much electricity is used by 90% of people or how likely they are to use a certain amount.
In a study of elephants a researcher wishes to determine the average weight of a certain subspecies of elephants From previous studies the standard deviation of the weights of elephants in this sub?
Elephants are losers
Suppose lifetime of certain type of car batteries are normally distributed. Brand A has a mean lifetime of three years and a standard deviation of six months. Brand B has a mean lifetime of 36 months and a standard deviation of four months?
Brand A
IQ scores are normally distributed with a mean of 100 and a standard deviation of 15 If a certain statistician has an IQ of 140 what percent of the population has an IQ less than she does?
99.6% for
IQ scores are normally distributed with a mean of 100 and a standard deviation of 15 if a certain statistician has an IQ of 140 what percent of the population has an IQ less than he does?
About 98% of the population.
The average amount customers at a certain grocery store spend yearly is 636.55 Assume the variable is normally distributed If the standard deviation is 89.46 find the probability that a randomly?
.820=82.0%
Why is it that only one normal distribution table is needed to find any probability under the normal curve?
Anything that is normally distributed has certain properties. One is that the bulk of scores will be near the mean and the farther from the mean you are, the less common the score. Specifically, about 68% of anything that is normally distributed falls within one standard deviation of the mean. That means that 68% of IQ scores fall between 85 and 115 (the mean being 100 and standard deviation being 15) AND 68% of adult male heights fall between 65 and 75 inches (the mean being 70 and I am estimating a standard deviation of 5). Basically, even though the means and standard deviations change, something that is normally distributed will keep these probabilities (relative to the mean and standard deviation). By standardizing these numbers (changing the mean to 0 and the standard deviation to 1) we can use one table to find the probabilities for anything that is normally distributed.
