sql query for mean,mode,median

[latha9]

Hi,

I need to find the score reported and no score reported for that I have written the following query and I got the result.

select count(case when va.ANSWER <= to_char(sysdate) then 1 end ) "Reported a Score",
count(case when (va.ANSWER is null or va.ANSWER > to_char(sysdate ,'mm/dd/yyyy')) then 1 end ) "No Score Reported"
from instrument i,dept_assessment da,v_assessment_answer va
where da.INS_ID=i.INS_ID
and va.INS_ID= i.INS_ID
and va.ASSMT_ID=da.ASSMT_ID
and va.INS_QUES_TXT='Date of LOCUS (mm/dd/yyyy)'


now I have to find out the the average,mode,median,high and low range for reported a score column.actually this is a date datatype and I am finding the count.i don’t understand how to find these.Can anyone suggest how to write a query for mode,mean,average,median,max and min.
when I use the following query I would get the records for “reported a score” column

select va.ANSWER
from v_assessment_answer va
where va.INS_QUES_TXT='Date of LOCUS (mm/dd/yyyy)'
and va.ANSWER <= to_char(sysdate)


Thanks,