UT School of Information - INF 397C: Mathematical Symbols, Rounding, and Significant Figures

∃	there exists, there are
IFF	if and only if
≡	is defined as
≠	is NOT equal to
>	is greater than, e.g., 9 > 5, 9 is greater than 5
≥	is greater than or equal to
<	is less than, e.g., 3 < 6, 3 is less than 6
≤	is less than or equal to
≈, ≅	is approximately equal to
∴	therefore
↓	rounded down (to the nearest integer/whole number); ↓9.5 = 9
	We use this particular convention only in the special case of calculating the median when N/n is even. In all other instances, the convention is that 1, 2, 3, or 4 round down to the next lowest number, while 5, 6, 7, 8, and 9 round up to the next highest number, e.g., 3.12 can be rounded to 3.1 or 3.0, 456 to 460 or 500, and 1,234 to 1,230 or 1,200 or 1,000, all depending upon the number of significant figures needed and allowed. For example, the number 11 has two significant figures, the number 2,003 has four significant figures, 2.3 has two significant figures, and 0.031 has three significant figures.

With regard to significant figures and performing calculations, a good heuristic to keep in mind is to add one (1) or at most two (2) significant figures to the number of significant figures in the data. Adding more results in false precision.