14. Report
14.1 Report the following information:
14.1.1 Report the dry vapor pressure equivalent to the nearest 0.1 kPa (0.01 psi) without reference to temperature.
14.1.2 If the sample was observed to be hazy in 8.5, report the test result as in 14.1.1, followed by the letter "H".
NOTE 6 - The precision and bias statements have not been determined for hazy samples, since these types of samples have not been evaluated as part of an interlaboratory study.
NOTE 7 - The inclusion of the letter "H" in 14.1.2 is intended to alert the data recipient that the sample analyzed was hazy. In the event a laboratory has a computer system that is incapable of reporting alphanumeric results according to the requirements in 14.1.2, it is permissible for the laboratory to report the result obtained as in 14.1.1, along with a statement or annotation that clearly conveys to the data recipient that the sample analyzed was hazy.
15. Precision and Bias
15.1 The precision of this procedure as determined by the statistical examination of interlaboratory test results is as follows: The following precision data were developed in a 1991 interlaboratory cooperative test program. Participants analyzed sample sets comprised of blind duplicates of 14 types of hydrocarbons and hydrocarbon-oxygenate blends. The oxygenates used were ethanol and MTBE. The oxygenate content ranged nominally from 0 to 15 % by volume and the vapor pressure ranged nominally from 14 to 100 kPa (2 to 15 psi). A total of 60 laboratories participated. Some participants performed more than one test method, using separate sample sets for each. Thirteen sample sets were tested by this test method using two different instruments, 26 sample sets were tested by Test Method D4953, 13 by Test Method D5190, and 27 by Test Method D5191. In addition, six sets were tested by modified Test Method D5190.
15.1.1 Repeatability - The difference between successive test results obtained by the same operator with the same apparatus under constant operating conditions on identical test material would, in the long run, in the normal and correct operation of the test method, exceed the following value only in one case in twenty:
1.31 kPa (0.19 psi) for HERZOG Model SC 970
1.79 kPa (0.26 psi) for ABB Model 4100
15.1.2 Reproducibility - The difference between two single and independent test results obtained by different operators working in different laboratories on identical test material would, in the long run, exceed the following value only in one case in twenty:
2.69 kPa (0.39 psi) for HERZOG Model SC 970
4.14 kPa (0.60 psi) for ABB Model 4100
15.2 Bias - Since there is no accepted reference material suitable for determining the bias for the procedures, bias cannot be determined.
15.3 Relative Bias - Statistically significant relative biases were observed in the 1991 interlaboratory cooperative test program between the total pressure obtained using instruments described in this test method and the dry vapor pressure obtained using Test Method D4953, Procedure A. These biases are corrected by applying Eq 1.
NOTE 8 - The bias and precision information provided for the ABB apparatus are applicable only for the instruments manual mode of operation, for a nominal vapor pressure range of 13.8 to 82.68 kPa (2 to 12 psi).
15.4 Reproducibility Between Methods - Just as the reproducibility supplies a 95 % confidence level on the difference between measurements by two different laboratories using the same method, there exists an equivalent reproducibility describing the 95 % confidence level on the difference between measurements by two laboratories using different methods.
15.4.1 A statistically based method for calculation of reproducibility between different methods was developed as listed below:
where:
R1, R2 = the reproducibility figures for each method under consideration, methods one and two, respectively, and
n1, n2 = the number of labs whose data was used to calculate R1 and R2, methods one and two, respectively. For this test method the number of labs is six.
16. Keywords
16.1 dry vapor pressure equivalent; gasoline; hydrocarbon-oxygenate blends; mini method-atmospheric; petroleum products; vapor pressure