--- loncom/html/adm/help/tex/Significant_Figures.tex	2013/07/05 18:30:40	1.3
+++ loncom/html/adm/help/tex/Significant_Figures.tex	2014/03/17 04:24:56	1.7
@@ -1,13 +1,39 @@
 \label{Significant_Figures}
-A \textbf{significant figures} specification tells the system how many significant
-figures there are in the problem, as either a single number or a range of
-acceptable values, expressed as \textbf{min,max}. The system will check to
-make sure that the student's answer contains this many significant digits,
-useful in many scientific calculations. For example, if the problem has three
-significant digits, the significant digit specification is {}``3'', and
-the answer is {}``1.3'', the system will require the students to type {}``1.30'',
-even though numerically, {}``1.3'' and {}``1.30'' are the same. A significant
-figure specification of {}``3,4'' means both {}``1.30'' and {}``1.300''
-are acceptable. The significant figures field can be deleted if you do 
+A \textbf{significant figures} specification is an optional setting that 
+tells LON-CAPA how many significant
+figures there are required for the answer, as either a single number, e.g. 3, or a range of
+acceptable values, expressed as \textbf{min,max}. The significant figures field can be omitted if you do 
 not want to constrain the number of significant digits in the student answers.
- 
+
+The system will check to
+ensure that the student's answer contains the required significant digits,
+useful in many scientific calculations. For example, if the computer answer is {}``1.3'',
+and the problem requests three significant digits, specified by (entered without quotes) 
+{}``3'',  the system will require the students to type {}``1.30'',
+even though numerically, {}``1.3'' and {}``1.30'' are the same. A significant
+figure specification of (entered without quotes) {}``3,4'' means both {}``1.30'' and {}``1.300''
+are acceptable. 
+
+Authors should be clear in the problem statements to tell students the required
+number or range of significant figures. If the student response does not contain 
+the correct number of significant digits, the LON-CAPA response will 
+tell students to increase or decrease the digits in their response, but it will not
+tell them how many digits to use. These responses do not use up
+the number of trials, but such responses are frustrating for students. If you would like to ensure
+that at least three significant digits are used, then a specification such as 3,15
+ensures at least three digits are used, but will quietly accept up to 15.
+
+Note that care must be used when using formatted computer answers together with 
+a significant digit specification.
+You must ensure that the formatted answer provides enough significant digits.
+To test the formatted answer, LON-CAPA converts the computer answer,
+as generated in the script block, according to the
+format attribute in the numericalresponse tag, e.g. 3f.
+Then LON-CAPA separately applies that number of significant
+figures to the computer answer, and if that result
+falls outside the range specified in the significant digit parameter, 
+it "grades" the computer answer as SIG\_FAIL (i.e., not correct). 
+It is a good idea to use the problem testing environment to test plenty of different
+randomizations to make sure that your format and sig digits parameters are compatible.
+This helps ensure that the formatted answer has enough significant digits.
+