> Of Chris KEENAN [use of mm] >Part of the problem is that it can lead to people to believe that >it confers an accuracy that isn't warranted
It is true that: 1. People often confuse precision and accuracy. 2. People think that the unit itself defines the precision and/or the accuracy. >so something that was a foot gets converted to 305.8 mm [I think you mean 304.8] It would follow to say "something that was a foot gets converted to 305 mm". The issue of additional decimals is slightly more complicated: 1. They are often appropriate when converting from small units to large units, but inappropriate in the other direction. People sometimes make the mistake of using the same number of significant figures in both directions. 2. People sometimes merely write what they see on their calculator. 3. People sometimes want to let you know that they have done the conversion using a great degree of precision. 4. Additional significant figures are often appropriate in intermediate calculations. People sometimes fail to make a distinction between intermediate and final precision. 5. People sometimes know all the above but sometimes do not care. 6. People want to make the converted value look silly. >Our opponents are quite happy giving examples such as >'a 453.5924 g of flesh' I am not too worried when people say '453.5924 g of flesh' because I don't think it is persuasive to British people who are 'floating voters' with regard to metrication. However, '454 g of flesh' is plausible and the UKMA website addresses the question of figures of speech. It is not, however, relevant to this debate about precision. It is interesting to use the example of mass because the criticism must surely apply to grams if they also apply to other units. British butter is in 250 g packs and delhi counters price 'per 100g'. Nobody ever suggests that gram values are 'unnecessarily large' or 'unfriendly' and that our butter should be labelled 25 cg and that the delhi should price 'per 10 cg'. >So I think we need to strike a balance between what we say is >recommended practice, and what is acceptable in everyday situations. What you say is entirely reasonable. Where there is no metric, then there is legitimate debate to have about which metric units should be used. The line of argument starts with a reasonable position "the metric system includes cm, make full use of them". However, the wording on the UKMA website goes well beyond that position. It makes specific criticisms of the metric policies of the joint committee in the 1960's, the building, engineering and catering industries. As far as I know, this is the only part of the UKMA website that contains text that is directly hostile to metric users and organisations. I am sure the same message could be put in a less aggressive manner.
