All values within the interactive map are displayed as percentile rank.  Percentile rank refers to the percentage of scores that are equal to or less than a given score.  It is a measure of how a tract compares to other census tracts for that indicator, Domain, or the Age-Friendly Community Index.  For example, if an indicator has a percentile of 60, this means that this census tract ranks 235 out the 392 populated census tracts.  This is interpreted as meaning that this census tract is higher than 60% of all the other census tracts in Allegheny County for that indicator.  Percentile ranks are used here simply as a statistical measure of where each census tract stands compared to other tracts within the county.

The indicators used to calculate the AFC index come from diverse sources and have varying underlying distributions.  Percentile rank calculations provide a useful way to describe data without making any assumptions about those distributions.  It is worth noting that a percentile does not describe the magnitude of difference between tracts, for example a tract ranked in the 75th percentile is not three times higher than a tract ranked in the 25th percentile.

When a tract has no indicator value (for example, the census tract has no public transit stops), it is excluded from the percentile calculation and assigned a score of zero for that indicator.  Thus, the percentile ranking can be thought of as a comparison of tracts where the age-friendly community characteristic is present.

Interactive AFCI Map