Search results
Results from the WOW.Com Content Network
These n h must conform to the rule that n 1 + n 2 + ... + n H = n (i.e., that the total sample size is given by the sum of the sub-sample sizes). Selecting these n h optimally can be done in various ways, using (for example) Neyman's optimal allocation.
Proportionate allocation uses a sampling fraction in each of the strata that are proportional to that of the total population. For instance, if the population consists of n total individuals, m of which are male and f female (and where m + f = n), then the relative size of the two samples (x 1 = m/n males, x 2 = f/n females) should reflect this proportion.
A related form are weights normalized to sum to sample size (n). These (non-negative) weights sum to the sample size (n), and their mean is 1. Any set of weights can be normalized to sample size by dividing each weight with the average of all weights.
In general, the subscript 0 indicates a value taken from the null hypothesis, H 0, ... = sample 1 size = sample 2 size ¯ = sample mean ...
Each stratum is then sampled as an independent sub-population, out of which individual elements can be randomly selected. [8] The ratio of the size of this random selection (or sample) to the size of the population is called a sampling fraction. [12] There are several potential benefits to stratified sampling. [12]
[2]: 277 If the organization elects to only inspect a fraction of units produced, the sample size should be chosen large enough so that the chance of finding at least one nonconforming unit in a sample is high—otherwise the false alarm rate is too high. One technique is to fix sample size so that there is a 50% chance of detecting a process ...
Get AOL Mail for FREE! Manage your email like never before with travel, photo & document views. Personalize your inbox with themes & tabs. You've Got Mail!
A riffle box is a box containing a number (between 3 and 12) of "chutes" - slotted paths through which particles of the sample may slide. The sample is dropped into the top, and the box produces two equally divided subsamples. Riffle boxes are commonly used in mining to reduce the size of crushed rock samples prior to assaying.