@Binky Sorry, I don't understand "sig. fig.s". ?
Significant Figures:
How precisely a number is recorded
The more precise a number, the more digits its worth quoting accurately.
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Example:
Suppose a national census receives 35,678,541 replies.
That probably isn't a perfect measure of how many people are in the country. Illegal immigrants, emigrants, etc. It could be off by a few thousands, so you might round it and say:
"The population of this country is 35,679,000"
That number is correct to five significant figures
If you asked me in conversation what the population was, I'd probably say
"About 36 million"
That would be correct to two significant figures.
If I were being really lazy, I might just say
"40 million"
Which is only correct to one sig fig.
In a scientific context, the number of sig figs used implies the precision of the value.
A weather-forecasting computer might predict that the wind speed at
16h 32m 06.422s today will be
21.639m/s
While that may be the mathematically precise result of the calculations involved, it would be inappropriate for those results to be published in that form, because weather forecasts are never that accurate. It would be far more reasonable to quote
16h30m and
20m/s when reporting the forecast.
When doing calculations, it is pointless (and misleading) to give answers that are more precise than the original data.
In the case at hand, the input data (number of Pyras sold so far) only has three digits - and people aren't buying fractional pyras. That means that FBnil's equation...
y = 112.3626812 ln(x) + 348.0876387
(Where y is number of Pyra preorders, and x is time)
...is unreasonable, because the prediction is not accurate to the nearest 0.0000001 Pyras!
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