Hi I am tring to make mapinfo display data through its quantiling feature. I have searched the Archive and read relavant material, i still have questions.
My understanding of statistical quantiling is: you are looking at the distribution of one variable as segmented by the arbitrary segmentation of another. eg: i want to look at the distribution of singleparent families across neighbourhoods. what i assume gets done is the data for single parents by neighbourhood is ranked and then you make a decision about the level of quantiling, say quartiles. the number (N) of neighbourhoods is divided by 4 and starting at the low end the program counts up the scale until it reaches the neighbourhood that represents the 25% of all neighbourhoods. the score for the lone parent variable is read, it then counts to the 50% neighbourhood and reads the score, 75% neighbourhood, etc. the cutpoints of the lone parent variable are determined by selecting an arbitrary and unbiased criteria, quartiles. interpretation would be:" for the lowest 25% of the neighbourhoods the range of single parent families is x%-xx%, for the next 25% of neighbourhoods the range is xx%-xxx%....." I would expect this map to have 4 groups of neighbourhoods with an equal (or nearly equal) number of neighbourhoods with each group consisting of 25% of the neighbourhoods and having a varing range of values for the loneparent variable. if the data was normally distributed then you could predict the ranges of the loneparent variable. however when i make this map in Mapinfo using the quantiling feature i do not get equal or nearly equal groups of neighbourhoods. what am i missing? do have to sort the data ahead of time? i was expecting Mapinfo to do that. can anyone enlighten me either to my bad statistical knowledge or to the correct working of this feature? thanks. Bill Holden Senior Planner Planning Research and Information Resource Centre City Planning Branch Community Services Department City of Saskatoon 306-975-2687 [EMAIL PROTECTED] Bill Holden Senior Planner Planning Research and Information Resource Centre City Planning Branch Community Services Department City of Saskatoon 306-975-2687 [EMAIL PROTECTED] _______________________________________________________________________ List hosting provided by Directions Magazine | www.directionsmag.com | To unsubscribe, send e-mail to [EMAIL PROTECTED] and put "unsubscribe MapInfo-L" in the message body.
