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| residency2009 Total Posts: 25 | Posted: Fri Oct 31, 2008 04:22 am Hi Can anybody pls explain how to arrive at the answer If the systolic blood pressure in a population has a mean of 130 mm Hg and a median of 140 mm Hg, the distribution is said to be? A) Symmetrical B) Positively skewed C) Negatively skewed D) Either positively or negatively skewed depending on the Standard deviation The answer given is C |
| bari Total Posts: 44 | Posted: Fri Oct 31, 2008 06:39 am let us first briefly see a standard normal curve * it is a bell shaped smooth curve * it has two tails and a hump * it does not touch the base line * MEAN = MEDIAN = MODE all coincide now any variation in either of the three variables will change the shape of the curve and the skewed distribution can be identified by the location of tail of the curve and not the hump. so when 1. mean = median = mode the curve will be bell shaped 2. mean < median < mode the curve will be left skewed or negatively skewed 3. mean > median > mode the curve will be positively skewed or right skewed. in the above question as mean is less than median it will be negatively skewed. i know its very difficult to catch up without diagrams but im not able to paste diagrams in this page. may be this of different format. for diagrams kindly see high yeid biostatics or psm & biostatics by deepak mishra third edition |
| residency2009 Total Posts: 25 | Posted: Fri Oct 31, 2008 02:00 pm Thanks Bari, You did a good job even without the diagrams. Appreciate your timely help Good Luck  |