When Figures Signify Nothing Jamil Ahmad University of Bahrain, P.o. Box 32038, Bahrain
Have you heard the one about the Egyptian tour guide who told his visitors that the pyramid they beheld in awe was 5007 years old. "Five thoisand and seven!" remarked someone. "Yes", said the guide. "When I first started here I was told i t was built 5000 years ago, and I've been here now 7 years." All around us we see the story replayed in one form or another. Sometimes it is less subtle, as in the lab report written by a student armed with a 10-digit calculator. At other times a bit of reflection is needed to discern the significant from the absurd. I am sure the readers have encountered examples like that below. The can of baked beans on the supermarket shelf labeled as 1lb net somehow also claims to contain 454 g-a confident, perhaps unintended and unjustifiable, claim to precision. The Oxford Atlas and the Britannica Atlas, among others, also fall into the trap of significant figures with the legends to their maps. Thus, a green area on one map indicates, according to the legend, an elevation not only of 1000-2000 m but also of 3281-6562 ft. A Bahraini newspaper, always eager to inform its readers on current finances, converts American dollars to the local currency, Bahraini Dinars (BD), in its news items. The result is stories like this:
... The damage to the building was estimated to be over $2 million (BD 754 000)...
Two cosmonauts went into orbit on a mission designed to turn a profit of more than $40 million (BD 15.08 million). ...
Perhaps the most amusing example is from a travel brochure that describes the majestic peaks of the Korakoram mountains. To inform both metrically literate and illiterate tourists, the authors make frequent conversions between feet and meters. To quote: The mighty glacier Baltoro fed by some 30 tributaries constitutes a surface area of 1219.39 sq. km (471 sq. miles). Of the fourteen 8000-m (26,246 ft) peaks on earth, four occupy an amphitheater a t the head of the Baltoro. There are scores of 7000-m (22965.87 ft) peaks in the Korakoram range and hundreds of nameless summits below 6096 m (20,000 ft), mere points on the map .... The Hindukush is also a vast mountain fastness containing hundreds of peaks, many above 7000 m (22,965.87 ft) including Trichimir 7787.64 m (22550 ft) which is the highest point of the range.
The same brochure goes on to describe the climate: The tourist season is from April to October. The maximum temperature is 26.67 C (80 F) and the minimum (October) 7.22 C (45 F)...
With such poor examples constantly before them, how can we expect our students to learn and remember the correct use of significant digits? Ironically, maybe these same poor examples can be the key to better education- when used to add humor.
Volume 68
Number 6
June 1991
469
