Quality assurance exercise
Bob’s coal mining company has submitted the June and July, 2013 coal questionnaires to the Alberta
statistical office. Your boss asks you to perform verifications of the questionnaire and gives you the
following checklist.
Please note your observations and also any improvements to the checklist that could be made.
a) Are opening and closing stocks from the two questionnaires consistent?
Need to assume stock on 28/30/31 is measured at midnight, and 1 = 28/30/31 from the prior
month.
In this case 2200, 2000 and 1290 differs from 2000, 2300 and 1200.
b) How does supply and demand balance for the various products in the July questionnaire?
Supply = 2710 ,1200 and 1650
Disposition = 1585, 1105 (95) and 1640 (10).
Matches with balancing adjustment for met coal and thermal coal, but NOT for raw coal.
Imports of raw coal quite strange in this case. Production is very close to total amount
processed, which makes the imports + receipts from other companies a bit odd. Why buy if
they cannot process?
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c) What observations can you make about raw coal supply and disposition for July?
6.1 <> 6.2
Import / receipt issue above.
1.1 resembles 1.2. OK.
Doesn’t handle raw coal in imports/receipts particularly well in exercise… Should be possible
the way the questionnaire is though, which is good.
d) What observations can you make about metallurgical coal supply and disposition for July?
All receipts/imports. (no prod)
Large stocks on hand. Odd to be importing when several month’s worth on hand already.
6.1 <> 6.2
Value data not provided.
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e) What observations can you make about thermal coal supply and disposition for July?
-losses from washing ~5%
- no price data
- issue with form where sub-items in closing inventory not available in opening inventory
which is very, very strange.
- Used 100% locally for electricity generation – this is very reasonable.
f)
What improvements could be made to this checklist to improve quality assurance?
Context:
-Need to check to rest of records in times series – concentrate on break in time series or large
swings.
-Need to collaborate with other provinces and companies to see if peer data fits.
-Need to be able to sell raw coal to 3rd party washers – happens in countries like India, or
ignore, but track shipping on consignment.
- Need to check reported sales to consumers with reported consumer data obtained
independently, particularly on the macro level.
-Need to check raw production > coking production+ thermal production over time.
-Check CVs calculated on correct basis. Net, gross, as is, etc.
-Check value/quantity to calculate price – check this is in range with prior contracts, spot
prices, peers from same time. Could even normalize by CV. Query outliers. Check met prices
are significantly higher than thermal.
Specifics:
-form designed to only take negative numbers in specific fields like stock changes and
balancing.
-check day one = last day of previous month for stocks.
-checks mandated on form including supply = disposition, 6.1 = 6.2, sub-totals = sum of parts
and totals = sum of sub-totals.
-closing = start – shipments + adjustments or whatever.
-(not essential but very odd if not true) – check that met coal used in coke ovens and thermal
coal used in the other uses. Ask reasons why if thermal used in coke production or coking coal
used in electricity generation. Some industries use coking coal. Still worth checking.
-check calorific data filled out.
-check calorific data higher for washed coal. (could import lower quality coal, but need to
check).
-check met CV > thermal.
- make formulas more obvious/ use conditional formatting.
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