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.
1 The retainer is based on an estimate of the number of hours of work that will be required; it might be $500-$2,000 for a simple project or $3,000-$10,000 or more for a complicated and time-consuming situation. Depending on the type of work done, the location and whether the case requires one investigator, two or more, the hourly rate can vary $40-$300 an hour but typically averages about $50-$100 an hour.