12-30-2008, 09:44 AM
In a normal distribution curve, what is the % of cases below 2 standard deviation below the mean......
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biostat QQQQQQ doubt pls - vlsr
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12-30-2008, 09:57 AM
it is given as 2.5% in kaplan..... im not able to understand????? any pls explain to me
12-30-2008, 10:01 AM
2SD covers 95% of cases. Now those that are left= 100-95= 5% including both above and below the mean. Thus dividing by 2: 5/2= 2.5% gives the % of cases below 2SD below the mean.
12-30-2008, 10:07 AM
thanQ..... i understood...but what is this concept of above and below......
what is meant by above 1s below the mean????? im confused....
12-30-2008, 10:09 AM
for this above 1s below the mean % of cases is given as 84%....
im not able to understand
12-30-2008, 11:01 AM
this is what i know...
suppose the mean ht of a community is 5 feet and each sd is 1 inch,then on sd on either side of mean ie 1 inch more and 1 inch less than 5 feet compises a 68%of population .so 34% of population have ht of 5ft 1 inch and 34% have 4 ft 11 inches.so 1sd below mean is 4ft 11 inches.same applies to 2 sd ,2sd below mean is 4ft 10 inches,2sd above mean is 5 ft 2 inches...so totally 2sd comprises 95.5%of population.i think u already knew this...i just told u what i hav understood
12-30-2008, 11:11 AM
yeh i understood that rule but im not able to corelate between that rule nd the above mentioned Qs?????
12-30-2008, 11:15 AM
In a curve mean is the central point. If u draw a curve it will be easier for u.Here is a picture of the curve that can help u.
http://www.hc-sc.gc.ca/fn-an/surveill/nu..._1-eng.gif Above 1s below the mean means -1sd ie u hav to refer to the cases above SD but which SD? +sd or -sd.. now that we can know by knowing if its below(-1sd) or above(+1sd) the mean. For +1sd and -1sd plz see the figure in above link. |
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