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Pooled variance is a method for estimating variance given several different samples taken in different circumstances where the mean may vary between samples but the true variance (equivalently, precision) is assumed to remain the same. A combined variance is a method for estimating variance from several samples, given the size, mean and standard deviation of each. Mathematically, a combined variance is equal to the calculated variance of the set of the data from all samples. See links.
When data is homogeneous over k independent samples of size n_i for i=1,2,...,k, the pooled variance is given by s_p^2=((n_1-1) s_1^2+(n_2-1) s_2^2+⋯(n_k-1) s_k^2)/(n_1+n_2+⋯+n_k-k)
Pooled resources and skills are
the use of essential and non-essential sentences
Favourable variance is that variance which is good for business while unfavourable variance is bad for business
Kingdoms of vegetals and animals are dominated by the carbon chemistry.
Negative price variance is when the cost is less than budgeted. Volume variance is a variance in the volume produce.
efficiency variance, spending variance, production volume variance, variable and fixed components
There are 7 variances associated with a budget ( which are generally calculated for controlling purposes) 1- Material Price variance 2- Material Quantity variance 3- Labor rate variance 4- Labor efficiency variance 5- Spending variance 6- Efficiency variance 7- Capacity variance
Variance analysis is something used primarily by small businesses. It is a method used by managers of small businesses to improve the performance of their companies.
1- Assuming this represents a random sample from the population, the sample mean is an unbiased estimator of the population mean. 2-Because they are robust, t procedures are justified in this case. 3- We would use z procedures here, since we are interested in the population mean.
If you know the population variance or if you have a very large sample then you could reliably use a Z test. Otherwise you should use a t test and use s^2 as an estimator for the population variance.