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Is the sum of an absolute value is the same of their absolute values?
The sum of the absolute values of two numbers is greater or equal than the absolute values of the sum. It will be equal if both are positive or both are negative; greater if one is positive and one is negative. Try it out with some sample numbers!
What does weighted average mean?
The weighted arithmetic mean is used, if one wants to combine average values from samples of the same population with different sample sizes: : The weights wi represent the bounds of the partial sample. In other applications they represent a measure for the reliability of the influence upon the mean by respective values. rhinostar
What is independent values?
sample data drawn from one population is completely unrelated to the selection of sample data from the other population.
If three samples have means of 10 20 and 15 what is their grand mean?
The grand mean can only be calculated if the three samples are of equal size. In this case, the grand mean is the mean of the three sample means. In this case, it would be (10+20+15)/3 = 15. However, in the sample sizes are not equal you must take the weighted mean. One option would be to assign, to each of the three means, an importance that reflects its sample size. So, if in the above example, the sample sizes were a, b and c the grand mean would be (10a + 20b + 15c)/(a+b+c) It is easy to show that the grand mean becomes the mean of the three sample means when a = b = c.
What is sample?
A sample is a subcollection of members selected from a population. (Ref Triola, Elementary Statistics). A sample may be real or hypothetical. Real- Ten patients at the hospital were interviewed about the care they received. Hypothetical- Repeatedly drawing n independent, and identical values X1, X2... Xn from a normal distribution to form a random sample, the mean of this sample should conform to a normal distribution, if the sample size is greater than 30.
Is the sum of an absolute value is the same of their absolute values?
The sum of the absolute values of two numbers is greater or equal than the absolute values of the sum. It will be equal if both are positive or both are negative; greater if one is positive and one is negative. Try it out with some sample numbers!
What is quantile group?
a group of equal proportions - the definition of quantile is one of a class of values of a variate that divides the total frequency of a sample or population into a given number of equal proportions
What does weighted average mean?
The weighted arithmetic mean is used, if one wants to combine average values from samples of the same population with different sample sizes: : The weights wi represent the bounds of the partial sample. In other applications they represent a measure for the reliability of the influence upon the mean by respective values. rhinostar
What is independent values?
sample data drawn from one population is completely unrelated to the selection of sample data from the other population.
What is measured by the pulling of gravity on a sample of matter?
The gravitational forces in each direction between the Earth and a sample of matterare equal. The force exerted on the sample by the Earth is what we call the "weight"of the sample. The force exerted by the sample on the Earth is the one that nobodyever mentions, but it's also equal to the weight of the sample. In other words, theweight of the sample on Earth is equal to the weight of the Earth on the sample.
What are quantitative techniques?
Many of the quantitative techniques fall into two broad categories: # Interval estimation # Hypothesis tests Interval Estimates It is common in statistics to estimate a parameter from a sample of data. The value of the parameter using all of the possible data, not just the sample data, is called the population parameter or true value of the parameter. An estimate of the true parameter value is made using the sample data. This is called a point estimate or a sample estimate. For example, the most commonly used measure of location is the mean. The population, or true, mean is the sum of all the members of the given population divided by the number of members in the population. As it is typically impractical to measure every member of the population, a random sample is drawn from the population. The sample mean is calculated by summing the values in the sample and dividing by the number of values in the sample. This sample mean is then used as the point estimate of the population mean. Interval estimates expand on point estimates by incorporating the uncertainty of the point estimate. In the example for the mean above, different samples from the same population will generate different values for the sample mean. An interval estimate quantifies this uncertainty in the sample estimate by computing lower and upper values of an interval which will, with a given level of confidence (i.e., probability), contain the population parameter. Hypothesis Tests Hypothesis tests also address the uncertainty of the sample estimate. However, instead of providing an interval, a hypothesis test attempts to refute a specific claim about a population parameter based on the sample data. For example, the hypothesis might be one of the following: * the population mean is equal to 10 * the population standard deviation is equal to 5 * the means from two populations are equal * the standard deviations from 5 populations are equal To reject a hypothesis is to conclude that it is false. However, to accept a hypothesis does not mean that it is true, only that we do not have evidence to believe otherwise. Thus hypothesis tests are usually stated in terms of both a condition that is doubted (null hypothesis) and a condition that is believed (alternative hypothesis). Website--http://www.itl.nist.gov/div898/handbook/eda/section3/eda35.htmP.s "Just giving info on what you don't know" - ;) Sillypinkjade----
If three samples have means of 10 20 and 15 what is their grand mean?
The grand mean can only be calculated if the three samples are of equal size. In this case, the grand mean is the mean of the three sample means. In this case, it would be (10+20+15)/3 = 15. However, in the sample sizes are not equal you must take the weighted mean. One option would be to assign, to each of the three means, an importance that reflects its sample size. So, if in the above example, the sample sizes were a, b and c the grand mean would be (10a + 20b + 15c)/(a+b+c) It is easy to show that the grand mean becomes the mean of the three sample means when a = b = c.
According to the normal probability distribution 95 percent of the values of a normal random variable are contained w in plus or minus how many standard deviations from the mean Why is that important?
Approximately 2 standard deviations (1.96, actually) from the mean. That is important to know that if one has a sample of 1000 values, if one selects a threshold at +/- 2 standard deviations from the mean, then one expects to see about 25 values exceeding those thresholds (on each side of the mean)
How does one calculate the standard error of the sample mean?
Standard error of the sample mean is calculated dividing the the sample estimate of population standard deviation ("sample standard deviation") by the square root of sample size.
Why is the standard deviation calculation for populations different than for samples and why is the denominator 'n' or 'n-1'?
1. Compute the square of the difference between each value and the sample mean.2. Add those values up.3. Divide the sum by n-1. This is called the variance.4. Take the square root to obtain the Standard Deviation.Why divide by n-1 rather than n in the third step above?In step 1, you compute the difference between each value and the mean of those values. You don't know the true mean of the population; all you know is the mean of your sample. Except for the rare cases where the sample mean happens to equal the population mean, the data will be closer to the sample mean than it will be to the true population mean.The value you compute in step 2 will probably be a bit smaller (and can't be larger) than what it would be if you used the true population mean in step 1. To make up for this, divide by n-1 rather than n.But why n-1?If you knew the sample mean, and all but one of the values, you could calculate what that last value must be. Statisticians say there are n-1 degrees of freedom.
What percent of members in a random sample have an equal chance of being selected?
100% or each one of them.
Can the five-number summary be used to calculate the standard deviation?
No. To calculate a sample standard deviation one requires the sample values. The five-number summary provides only the lowest value, the highest, the median, and the upper and lower quartiles. In any sample of size greater than five some values will be missing from the summary.
