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1.1     ! matthew     1: \label{Statistics_Cache}
        !             2: 
        !             3: The \textbf{\index{Statistics Cache}Statistics Cache} manages the data 
        !             4: used in computing student performance statistics.
        !             5: 
        !             6: Much of the time spent computing statistics is actually used to
        !             7: compile student data into a more useful format, the temporary course
        !             8: cache.  Normally student data is maintained in an archived format
        !             9: which does not provide for rapid access.  Since each student's data is
        !            10: stored on their home server in their account, and not with the course,
        !            11: it takes time to compile the data and store it in the temporary course
        !            12: cache.  All of the statistics modes use the same cache so the process
        !            13: of compiling the student data does not need to be repeated when
        !            14: successive statistics are requested.
        !            15: 
        !            16: Only those students who are involved in the current calculation will
        !            17: have their data compiled.  When you modify the selected set of
        !            18: students, by changing the section you are computing statistics with,
        !            19: the caches will be updated.
        !            20: 
        !            21: The temporary course cache is maintained for 2 days on the server used
        !            22: for the statistics computation.
        !            23: 
        !            24: The cache management buttons, marked \textbf{Clear Caches} and
        !            25: \textbf{Update Caches}, appear when the temporary course caches are in
        !            26: use.  \textbf{Clear Caches} causes the entire cache for the course to
        !            27: be flushed, discarding all the current contents.  The cache is then
        !            28: rebuilt to display the desired statistics.  The normal use of
        !            29: statistics should not require you to press this button, but it is here
        !            30: for completeness.
        !            31: 
        !            32: \textbf{Update Caches} checks the students record for updates since their 
        !            33: data was compiled.  Any changes to the student's record for your
        !            34: course will be reflected after this button has been pressed.  The
        !            35: \textbf{Update Caches} button is useful if your students are currently
        !            36: completing a homework set and you wish to evaluate their progress in
        !            37: the time your statistics were generated.
        !            38: