E Standard Practice for Calculating Sample Size to Estimate, With Specified Precision, Standard + Redline PDF Bundle ASTM License Agreement. E - 09 Standard Practice for Calculating Sample Size to Estimate, With Specified Precision, the Format, Pages, Price. PDF ASTM License Agreement. E - Designation: E – 00 An American National Standard Standard Referenced Documents ASTM Standards: E De?nitions of.
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E - 09e1 - Download as PDF File .pdf), Text File .txt) or read online. ASTM. ASTM E Sample Size Determination. Uploaded by. Verónica Margarita . 9. Sample Size and Confidence. • Calculating Sample Size (ASTM: E - 09). • Demonstrating Confidence in Complying with an Acceptance Procedure (ASTM: . Historical Standard: ASTM E Standard Practice for Calculating Sample Size to Estimate, With Specified Precision, the Average for a Characteristic of a Lot.
Precision Desired 6.
That is, it must be decided what maximum deviation, E, can be tolerated between the estimate to be made from the sample and the result that would be obtained by measuring every unit in the lot or process. Equations for Calculating Sample Size 7. The choice of the factor 3 is recommended for general use. With the factor 3, and with a lot or process standard deviation equal to the advance estimate, it is practically certain that the sampling error will not exceed E.
Where a lesser degree of certainty is desired a smaller factor may be used Note 1. NOTE 1—For example, the factor 2 in place of 3 gives a probability of about 45 parts in that the sampling error will exceed E.
Although distributions met in practice may not be normal Note 2 , the following text table based on the normal distribution indicates approximate probabilities: Factor 3 2. There are two things to do when asymmetry is suspected.
If the relative error, e, is to be the same for all values of? The sample size for estimating the average of the? The average of these three standard deviations is psi. The standard deviation, s, from any given sample is computed as:?
An average of the? A better, more stable value for so may be computed by pooling the s values obtained from several samples from similar lots. The pooled s value sp for k samples is obtained by a weighted averaging of the k results from use of Eq 5.
The calculated s value will in general be a slightly biased estimate? An unbiased estimate of so is computed as follows: s?
However, the values of estimated standard deviation are approximately proportional to the observed averages, as shown in the following text table: Lot No. If this is not known, obtain this information from some other source.
Try to picture how the other observed values may be distributed. A few simple observations and questions concerning the past behavior of the process, the usual procedure of blending, mixing, stacking, storing, etc. In case of doubt, or in case the desired precision E is a critical matter, the rectangular distribution may be used.
E - 09e1
The price of the extra protection afforded by the rectangular distribution is a larger sample, owing to the larger standard deviation thereof. This method of advance estimation is acceptable and is often preferable to doubtful observed values of s, s, or r.
The values were heaped up in the middle of this band, but not necessarily normally distributed. Then A Values of standard deviation, s, may be used instead of the estimates made from the range, if they are preferred or already available.
The use of s would be more efficient. The data supplied by the prescribed sample will be useful for the study in hand and also for the next investigation of similar material.
Then for the weighted average use the following equation: p 5 total number nonconforming in all samples total number of units in all samples 12 8.
Nonconforming 3 10 4 4 21 Fraction onconforming 0.
Turn to Fig. In case the desired precision is a critical matter, use the largest value of so2 within the possible range of p8. Consideration of Cost If the cost is too great, it may be possible to relax the required precision or the equivalent, which is to accept an increase in the probability Section 7 that the sampling error may exceed the maximum allowable error E and to reduce the size of the sample to meet the allowable cost.
The same may be done for Eq 2 and Eq 3. If the value of E were 0. Turn to Fig.
In case the desired precision is a critical matter, use the Same or Like Material Available largest value of o2 within the possible range of p'. Consideration of Cost for Sampling and Testing computation of o. If the cost likely to be.
If this is not known, obtain this information from is too great, it may be possible to relax the required precision NOTE 1What is shown here for the normal distribution is somewhat arbitrary, because the normal distribution has no finite endpoints.
Selection of the Sample An acceptable procedure to ensure a random selection is the use random numbers. Lack of predictability, such as a mechanical arm sweeping over a conveyor belt, does not yield a random sample.
Moreover, each sampling unit must be identifiable by a serial number, actual, or by some rule. For packaged articles, a rule is easy; the package contains a certain number of articles in definite layers, arranged in a particular way, and it is easy to devise FIG. In the case of bulk material like ore, or coal, or a barrel of bolts or nuts, the or the equivalent, which is to accept an increase in the problem of defining usable sampling units must take place at an probability Section 7 that the sampling error may exceed the earlier stage of manufacture or in the process of moving the maximum error E and to reduce the size of the sample.
The discover the way to a satisfactory type of sampling unit.
Kategorie - podobné normy:
Instead, it is assumed that a suitable sampling unit has been ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentioned in this standard.If so, an estimate of the average value of that characteristic or of the fraction of the observed values that do not conform to a specification for that characteristic becomes a measure of quality with respect to that characteristic. This practice will astm e indicate the sample size required to astm e the average value of some property or the fraction of nonconforming items produced by a production process during the time interval covered by the random sample.
Last previous edition E— In other words, information concerning the process, and the material produced thereby, accumulates and should be used.
Your comments will receive careful consideration at a meeting of the responsible technical committee, which you may attend.
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