Consequently, in order to
monitor the accuracy of Bill of Lading or Outturn quantities, it is
possible to use the vessel quantities for comparative purposes.
This appendix provides two
alternative methods for calculating Vessel Experience Factors.
The parties involved should
agree on the method to be used.
 Data
Qualification / Rejection
Going by general statistical
rules, the greater the number of sets of data which are included, the
greater will be the confidence in the VEF established.
In practice, an adequate level
of confidence will be achieved when the final VEF calculation is based
on data from a specified minimum number of qualified voyages.
Using Method 1, data from a minimum of five (5) qualified voyages is
needed to calculate a VEF. However, a larger number is
desirable. Using Method 2, data from a minimum of ten (10)
qualified voyages is needed to calculate a VEF with the greatest
accuracy.
Because on occasions the
available data can give rise to nontypical VLRs or VDRs or because
essential information is missing, both calculation methods employ
techniques to ascertain the validity of a particular cargo lift VLR or
VDR before inclusion as a qualified voyage in the VEF calculation, else
it is rejected.
Method 1 excludes 

Voyages where shore
measurements were not available.

Voyages prior to structural
modification which affected the vessel's cargo capacity.

Voyages when the VLR or VDR is
not within +/0.3% of the ration of the totals of vessel and shore
quantities, for all the voyages under consideration.
Method 2 
Employs rigorous statistical
methods for establishing the reliability of individual load (or
discharge) ratios and for estimating the confidence limits (probability
of 95%) for the range of acceptable values.
Calculation of Vessel Experience Factor  Loading (Discharge
proceeds in a like manner)
Method 1  Uses a sequential
voyage log (form).

List the voyages data (for
voyages not disqualified basis the above paragraphs) under the
following column headers  Voyage Sequence (beginning with the last);
Cargo Name; Terminal; Date; Sailing (Arrival) TCV; Optional OBQ (ROB);
Load (Discharge) TCV, Shore TCV, VCF Tables Used.

Calculate Total Vessel Quantity
and Total Shore Quantity from the individual voyage quantities recorded
in Load TCV and Shore TCV.

Calculate the average
vessel/shore ratio from the total quantities.

Calculate individual VLRs for
each voyage and record in the next column  Vessel Ratio (Vessel TCV /
Shore TCV).

Check whether VLRs qualify 
Y/N in the next column (Y/N). (VLRs outside +/0.3% from the
average Vessel/Shore ratio determined in step 3).

Transfer qualifying voyage
numbers from Column 1 to the next column (Qualified Voyage No.) and the
corresponding vessel and shore TCV figures to the next two
columns. Total these two columns.

Divide the new total vessel
quantity by the new total shore quantity.

Calculate to five (5) decimal
places and report to four (4) decimal places the Vessel Experience
Factor as established in step 7.
Use this VEF to monitor the
Bill of Lading or Outturn Figure. Agreed limits may be
applied to monitor the Bill of Lading or Outturn.
Notes:

List last voyage first

Use same units for all entries

Do not mix load and discharge
figures

The average TCV ratio is equal
to the Total Vessel TCV divided by the Total Shore TCV

The form should be prepared
taking information from the Voyage Analysis Report (VAR), if available
Purchase SNsVEF where API, IP
and Statistical Methods (Method 2) are included in the coding.
Sections of text taken from API  MPMS Chapter 17 Marine Measurement
