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1.1       matthew     1: \label{Statistics_Key}
                      2: 
1.2       www         3: The \textbf{Overall Problem Statistics} page displays the following 
1.1       matthew     4: data about the problems currently in the course:
                      5: 
1.6       matthew     6: \begin{description}
1.1       matthew     7: 
1.6       matthew     8: \item{\textbf{\#Stdnts}} Total number of students attempting the problem.
1.3       matthew     9: 
1.6       matthew    10: \item{\textbf{Tries}} Total number of attempts to solve the problem.
1.1       matthew    11: 
1.6       matthew    12: \item{\textbf{Max Tries}} Largest number of attempts to solve the problem by a student.
1.3       matthew    13: 
1.6       matthew    14: \item{\textbf{Mean Tries}} Average number of attempts.
1.1       matthew    15: 
1.6       matthew    16: \item{\textbf{S.D. tries}} Standard Deviation of the tries.
1.3       matthew    17: 
1.6       matthew    18: \item{\textbf{Skew Tries}} Skewness of the students tries.
1.7     ! felicia    19: \[ \frac{\sqrt{ \sum{(Xi - Mean)^3} / \#Stdnts}}{\sigma^3} \]
1.1       matthew    20: 
1.6       matthew    21: \item{\textbf{\#YES}} Number of students who solved the problem correctly.
1.1       matthew    22: 
1.6       matthew    23: \item{\textbf{\#yes}} Number of students who solved the problem by override.
1.1       matthew    24: 
1.6       matthew    25: \item{\textbf{\%Wrng}} Percentage of students who tried to solve the problem but were unable to.
1.3       matthew    26: 
1.6       matthew    27: \item{\textbf{DoDiff}} Degree of Difficulty of the problem.  
1.1       matthew    28: 
1.6       matthew    29: This statistics gives a measure of how many attempts it took the
                     30: students to get the problem correct.  Those students who did not get
                     31: the problem correct are not counted.  A value close to 0 indicates
                     32: most students who got the problem correct did so on the first attempt.
                     33: A value close to 1 indicates many attempts were required for students
                     34: to get the problem correct.  A negative value indicates students were
                     35: given points without attempting the problem.  A value of 'nan' means
                     36: there were no attempts made on the problem.
1.3       matthew    37: 
                     38: \[ 1 - \frac{\#YES+\#yes}{Tries} \]
                     39: 
1.6       matthew    40: \item{\textbf{DoDisc}} Degree of Discrimination of the problem.
1.3       matthew    41: 
                     42: The students are grouped based on their scores on the sequence which 
                     43: contains the homework problem.  The percent score of the bottom 25\% of
                     44: the students is subtracted from the percent score the to top 25\% of
                     45: the students.  This yields a number from -1 to 1. 1.0 indicates
                     46: all of the good students answered the problem correctly and none of the
                     47: poor students answered it correctly.  Conversely, a score of -1.0 indicates
                     48: all of the good students got the problem wrong and the bad students did
                     49: well.
1.1       matthew    50: 
1.6       matthew    51: \item{\textbf{weight}} The weight of the problem in the course (``points'').
                     52: The value shown is the weight of the problem for the individual computing the
                     53: statistics.  Individual student or section variations are not shown.
                     54: 
                     55: \end{description}
                     56: 
                     57: \textbf{Sequence Statistics}, that is compiled statistics on problems based on
                     58: their containing sequence, are also shown.  The following data are shown:
                     59: 
                     60: \begin{description}
                     61: 
1.7     ! felicia    62: \item{\textbf{\#Items}} The number of problem parts in the sequence.
1.6       matthew    63: 
                     64: \item{\textbf{Score Mean}, \textbf{Score STD}, \textbf{Score Max} \textbf{Score Min}}
                     65: The mean, standard deviation, maximum, and minimum of the scores of
                     66: the selected students on the given sequence.
                     67: 
                     68: \item{\textbf{Score N}}  The number of the selected students who submitted answers to problem parts in the sequence.
                     69: 
                     70: \item \textbf{Count Mean}, \textbf{Count STD}, \textbf{Count Max}, \textbf{Count Min} 
                     71: The mean, standard deviation, maximum, and minum count of correct
                     72: problem parts of the selected students on the given sequence.
                     73: 
                     74: \item \textbf{Count N} The number of the selected students who submitted answers to problem parts in the sequence.
                     75: 
                     76: \item \textbf{KR-21} The KR-21 reliability statistic measures the internal reliability of a test or exam.
                     77: 
                     78: To compute the KR-21 reliability statistic the following formula is used:
                     79: 
                     80: \[KR-21 = \frac{K}{K-1} \cdot \frac{1-(M \cdot (K-M))}{K \cdot s^{2}}\]
                     81: 
                     82: Where 
                     83: \begin{description}
                     84: \item{$K$} is the number of items in your test
                     85: \item{$M$} the mean score on the test
                     86: \item{$s$} the standard deviation of the scores on your test
                     87: \end{description}
                     88: 
                     89: \end{description}