1 The median is the middle value of the data set. 2  The lower quartile (Q 1) is the median of the lower half of the data set. 3  The upper quartile (Q 3) is the median of the upper half of the data set. 4  The interquartile range (IQR) is the spread of the middle 50% of the data values.
Removable Essix retainers typically cost between $100-$250 for one or $200-$500 for two. They are made from a vacuum sealed clear plastic that is less noticeable but more likely to break or warp, meaning that you could be paying the price more than once for this style of retainer.
As KFF also points out, costs continue to vary greatly for Medicare Part D plans. Among the 10-most enrolled plans in 2016, the average monthly premiums in 2017 range from a low of $16.81 a month for the Humana Wal-Mart Rx plan, which works out to just over $200 a year, to $71.66 monthly for the AARP Medicare Rx Preferred plan, which works out to about $860 annually.