Dave wrote this: I was reading the combinations/permutations area of your web page and have a query. You mention that if a bank was allocating 4 digit pins then the number of possible pin numbers would be 5040. I don't understand why. If they can have 0000,0001.....9999, then why are there not 10,000 possible numbers? i.e. 9999 + 1 for 0000 any help would be great cheers dave Good question Dave that shows that I didn't explain that bit of that page fully, so I added a couple of examples to help out. Take a look at my Permutations and Combinations page to see the improvements I made. Thanks for helping out, Dave. DW

A problem that arises once a month or so is that someone writes to me with a question or other request which I deal with only to find that the email address they gave me doesn't work. Come on down OEMKY! Oemky wrote to ask for a spreadsheet but when I sent it, whoosh it came back. In case the in box was full at the other end I wrote again to ask them to empty their in box or provide an alternative address but whoosh that came back too. Please provide a valid email address for all replies, please. DW

Another unsolicited testimonial came in from a satisfied customer yesterday evening. Jerry said: Thank you! What more do I need to say! I have been in test engineering for years now and have been dodging to learn statistical maths for along time now! I have worked with various maths including differential equations and some FFT equations. My previous company was low volume wafer (Research and only program managers who tried to save their programs would do statistical maths) I could simply depend on trouble shooting on a real time bases, one by one real time failures. Now that I am in the Market, Test Engineers like myself have to know statistical maths and bell curve troubleshooting. Even though I could make an argument that they need to depend on common logic (circuit debugging and practical knowledge) for failure analysis. Test engineers in today's world need to analyze failure by measured percentages and how to rectify the numbers. I give in and here is my thanks to you. After reading the simple version on Mr. Niles I ran across your web site and found your problems. Ye old familiar symbol of sigma and found the maths not to complex. It seemed very similar in averaging Impedances in complex conjugates. Anyhow I simulated my own data sets of Currents for applied voltages of VBEE simulating some failures and BAM. I am ready to trouble shoot in series now. Just wanted to thank you for easy explanation. Aw, I've come over all embarrassed and shy! DW

Another gap in my literary ambitions. Here are a couple of things, though. Firstly, yesterday was sunny and fairly warm so I was able to tart up part of the garden. Then it lashed it down and I felt happy that I'd beaten the weather. Today was very wet again, which is just about par for a British Bank Holiday, as was today. Then the sun came out late in the afternoon. At which juncture I took to draining the hot water tank since it has been dripping for too long and I was living in fear of it leading to damp in the living room. Done and dusted now with no perceptible problems! Take a look at this that I came across and put together for a discussion list for teachers of business and economics: Anyone interested in some aspects of real live cost accounting, activity based costing in the Royal Mail in particular? There, that’s got rid of most of them! Here’s an ABC case study that is based on a topical issue, has excellent resources available completely free of charge, will enhance understanding of an ABC debate and can use role play as a central vehicle for learning, comprehension, application, analysis and synthesis. The case concerns the application of cost driver analysis and application at, wait for it, the Royal Mail. Surprised that a State owned organisation is using its information and logistical system properly? Be surprised no more and take a look at this page (http://news.bbc.co.uk/1/hi/business/3660571.stm) from the BBC to see how the Royal Mail has realised that the weight based cost driver for letters and packets is no longer appropriate as the basis for calculating selling prices: maybe it was never appropriate. So now they have moved to a volume based cost/price mechanism and this proposal is known as Sized Based Pricing (SBP). Get the students to find out who and what Postcomm is since the Royal Mail applied to Postcomm in August 2003 for them to consider this change. The time frame for this review must be excruciatingly slow for the Royal Mail as it has taken until now for Postcomm to begin the process proper. In this Crown Copyright PDF dated 27 April 2004, http://www.postcomm.gov.uk/documents/competition/SBPsummary.pdf (Royal Mail’s Proposal to Introduce Size Based Pricing A Summary Document April 2004) Postcomm says: Following this further work, there will be a second consultation document, which will set out the responses to the first consultation and give Postcomm’s proposed decision on whether, and if so how, SBP should be introduced. It will also focus on the cost justification for Royal Mail’s proposal. Royal Mail will be required, amongst other things, to demonstrate that implementing its proposal would lead to prices that are more closely in line with its costs than the present weight-based pricing structure. The cost information provided so far by Royal Mail has not been sufficiently robust for Postcomm to reach a decision on this issue. The above PDF sets out the Royal Mail case for change: ideal lesson materials in which the students can be given paragraphs 6 – 10 and then analyse them with respect to the Royal Mail proposals for applying their case for change in paragraphs 11 – 17. Quite simply, the Royal Mail is saying that costs vary more in proportion to volume than they do to weight. You could set up some basic exercises to demonstrate this effect if you wished. There are further resources at Postcomm (http://www.postcomm.gov.uk/Index2.html), such as this Crown Copyright PDF file dated 26 April 2004, http://www.postcomm.gov.uk/documents/Media/042604SBPPN.pdf. (Royal Mail wants size to matter) In that file you can read that the proposed changes are designed to be revenue neutral … there’s some jargon to lighten up your lives. They also say: “These proposals would involve major changes. They mean that light but large mail such as very large greetings cards, CDs, rolls of photographic film, audio cassettes and video tapes, would cost more to post, but that some heavier items – books for example – would cost less. I hope as many people as possible will let us know what they think.” Royal Mail has suggested three sizes for a letter, a large letter and a packet.

• A letter is mail that would fit into an envelope 165mm x 240mm (approx 6½in x 9½in) and not more than 5mm (approx. 3/16 in) thick
• A large letter is mail that would fit into an envelope 250mm x 353mm (approx 9¾in x 14 in) and not more than 10mm (approx. 3/8 in) thick
• A packet is mail that either measures more than 250mm x 353mm or is thicker than 10mm.

If you worry at all about the consequences of interference in State owned organisations, take a look at what I think is an astounding paragraph in the document http://www.postcomm.gov.uk/documents/competition/SBPsummary.pdf (Royal Mail’s Proposal to Introduce Size Based Pricing A Summary Document April 2004) S19. Postcomm recognises, however, that Royal Mail’s proposal is a major change to its pricing structure. Its weight based pricing structure has been in place since the 19th century and many businesses and postal users have evolved their behaviour and business models to fit with this pricing policy. Is Postcomm really saying that because a pricing structure has been in place for over 100 years that it must stay in place irrespective of whether it is, or ever was, appropriate? Could be by the look of it. Postcomm have told us in their SBP Summary document that they have S29. Since Royal Mail’s application, Postcomm has met some trade associations (including the Greeting Cards Association, Intellect, the Mail Order Photofinishers Association, the Mail Users Association and the Periodical Publishers Association) and companies affected by Royal Mail’s SBP proposals. You can set up a three way role play in which students can take the role of

• the Royal Mail’s cost accountant
• Postcomm
• Trade Associations

and see what they can come up with. Marvellous! By the way, it's worth taking a look at the Postcomm pages since there are other reports that are worth downloading relating to this topic. Then there's this that I posted to the same discussion list later on in the same week: Two reports of note on our Public Libraries that will help to explain why the public sector might need a level of reform that is currently beyond comprehension. Tim Coates is a leading light in book selling and he has spent four years researching the ways in which our public libraries, in particular in Hampshire, are working. He tells us that only 9 pence in the £ spent on libraries comes back to us in the form of books: the rest is eaten up in admin and other things, some of which are useful for the end user and others aren’t. Similarly, Coates says that 20% of all money spent on Public Libraries is wasted. See Appendix 2 of the report for the financial data. Be very worried by these extracts from Appendix 3: acquisition costs A total of £2.0m of the total library service budget of £19-20m is probably spent on the Acquisition supply chain. The actual amount spent on books in the year 2003/4 will be £1.4m. Thus, the total cost of books and the various acquisition processes is £3.4m. In simple terms and after allowing for book purchase discounts, Hampshire spends over £24 every time it buys a £10 book. This is broadly in line with figures actually measured in other authorities. It is far too high a cost. Report pages 28 and 29 You can download Coates’ report from http://www.rwevans.co.uk/libri/downloads.htm. One statistic that Coates includes that is a candidate for the rubbish bin can be found on page 5 of his report: for HTML recipients of this message, here’s the graph he presents: Talk about believing all you read in the newspapers! Ask your students to say why the projections contained in this bar chart are probably rubbish. Sorry for the emotive language but I think it’s an irresponsible outburst of hyperbole on Coates’ part! Otherwise, the report is worth skimming for ideas for business and, of course, accounting: there are lots of management accounting ideas buried in this report. For a summary of the report, see yesterday’s Daily Telegraph: sorry I didn’t take a note of the page but I did scan the article for my own purposes should anyone want to borrow it! Charles Leadbeater has also written on the subject of Public Libraries, for Demos this time; and his report, which is nowhere near as comprehensive as Tim Coates’ report, is also available for download free of charge at http://www.demos.co.uk/catalogue/default.aspx?id=262 DW