INF 397C - Professor Doty, Introduction to Research in Information Studies

Mathematical Symbols, Rounding, and Significant Figures


image2 there exists, there are
IFF if and only if
image 4 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
image 6  
image 8 is approximately equal to
image 10 therefore
image12 rounded down (to the nearest integer/whole number);
  image 12a9.5 = 9

This particular convention will be used 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.

Dr. Philip Doty, 512.471.3746 (office), pdoty at
TA: Paul Stenis, p.stenis at
| ©2007 Philip Doty