[LON-CAPA-cvs] cvs: loncom /html/adm/help/tex Statistics_Overall_Key.tex

[matthew]

matthew		Mon Mar 28 16:32:12 2005 EDT

  Modified files:              
    /loncom/html/adm/help/tex	Statistics_Overall_Key.tex 
  Log:
  Bug 3801: Need more help on statistics.  Also changed from 'itemize' list to
  'description' list.
  
  
Index: loncom/html/adm/help/tex/Statistics_Overall_Key.tex
diff -u loncom/html/adm/help/tex/Statistics_Overall_Key.tex:1.5 loncom/html/adm/help/tex/Statistics_Overall_Key.tex:1.6
--- loncom/html/adm/help/tex/Statistics_Overall_Key.tex:1.5	Mon Jan 10 13:01:30 2005
+++ loncom/html/adm/help/tex/Statistics_Overall_Key.tex	Mon Mar 28 16:32:11 2005
@@ -3,53 +3,41 @@
 The \textbf{Overall Problem Statistics} page displays the following 
 data about the problems currently in the course:
 
-\begin{itemize}
+\begin{description}
 
-\item \textbf{\#Stdnts}
+\item{\textbf{\#Stdnts}} Total number of students attempting the problem.
 
-Total number of students attempting the problem.
+\item{\textbf{Tries}} Total number of attempts to solve the problem.
 
-\item \textbf{Tries}
+\item{\textbf{Max Tries}} Largest number of attempts to solve the problem by a student.
 
-Total number of attempts to solve the problem.
+\item{\textbf{Mean Tries}} Average number of attempts.
 
-\item \textbf{Max Tries}
+\item{\textbf{S.D. tries}} Standard Deviation of the tries.
 
-Largest number of attempts to solve the problem by a student.
-
-\item \textbf{Mean Tries}
-
-Average number of attempts.
-
-\item \textbf{S.D. tries}
-
-Standard Deviation of the tries.
-
-\item \textbf{Skew Tries}
-
-Skewness of the students tries.
+\item{\textbf{Skew Tries}} Skewness of the students tries.
 \[\frac{\sqrt{ \sum{(Xi - Mean)^3} / \#Stdnts}}{\sigma^3}\]
 
-\item \textbf{\#YES}
+\item{\textbf{\#YES}} Number of students who solved the problem correctly.
 
-Number of students who solved the problem correctly.
+\item{\textbf{\#yes}} Number of students who solved the problem by override.
 
-\item \textbf{\#yes}
+\item{\textbf{\%Wrng}} Percentage of students who tried to solve the problem but were unable to.
 
-Number of students who solved the problem by override.
+\item{\textbf{DoDiff}} Degree of Difficulty of the problem.  
 
-\item \textbf{\%Wrng}
+This statistics gives a measure of how many attempts it took the
+students to get the problem correct.  Those students who did not get
+the problem correct are not counted.  A value close to 0 indicates
+most students who got the problem correct did so on the first attempt.
+A value close to 1 indicates many attempts were required for students
+to get the problem correct.  A negative value indicates students were
+given points without attempting the problem.  A value of 'nan' means
+there were no attempts made on the problem.
 
-Percentage of students who tried to solve the problem but were unable to.
-
-\item \textbf{DoDiff}
-
-Degree of Difficulty of the problem.  
 \[ 1 - \frac{\#YES+\#yes}{Tries} \]
 
-\item \textbf{DoDisc}
-
-Degree of Discrimination of the problem.
+\item{\textbf{DoDisc}} Degree of Discrimination of the problem.
 
 The students are grouped based on their scores on the sequence which 
 contains the homework problem.  The percent score of the bottom 25\% of
@@ -60,4 +48,42 @@
 all of the good students got the problem wrong and the bad students did
 well.
 
-\end{itemize}
+\item{\textbf{weight}} The weight of the problem in the course (``points'').
+The value shown is the weight of the problem for the individual computing the
+statistics.  Individual student or section variations are not shown.
+
+\end{description}
+
+\textbf{Sequence Statistics}, that is compiled statistics on problems based on
+their containing sequence, are also shown.  The following data are shown:
+
+\begin{description}
+
+\item{\textbf{#Items}} The number of problem parts in the sequence.
+
+\item{\textbf{Score Mean}, \textbf{Score STD}, \textbf{Score Max} \textbf{Score Min}}
+The mean, standard deviation, maximum, and minimum of the scores of
+the selected students on the given sequence.
+
+\item{\textbf{Score N}}  The number of the selected students who submitted answers to problem parts in the sequence.
+
+\item \textbf{Count Mean}, \textbf{Count STD}, \textbf{Count Max}, \textbf{Count Min} 
+The mean, standard deviation, maximum, and minum count of correct
+problem parts of the selected students on the given sequence.
+
+\item \textbf{Count N} The number of the selected students who submitted answers to problem parts in the sequence.
+
+\item \textbf{KR-21} The KR-21 reliability statistic measures the internal reliability of a test or exam.
+
+To compute the KR-21 reliability statistic the following formula is used:
+
+\[KR-21 = \frac{K}{K-1} \cdot \frac{1-(M \cdot (K-M))}{K \cdot s^{2}}\]
+
+Where 
+\begin{description}
+\item{$K$} is the number of items in your test
+\item{$M$} the mean score on the test
+\item{$s$} the standard deviation of the scores on your test
+\end{description}
+
+\end{description}