Quartiles are the measures of relative standing that divide a set of data into four groups, with 25 percent of the data in each group. For example, to find the quartiles from a bodyweight survey of various cat species, first, arrange the data from lowest to highest. Then, find the value that separates the lower 50 percent of the data from the upper 50 percent. This is the second quartile or median. The first and third quartiles are calculated using this formula. For first quartile, formula yields 2.5th value. It means the first quartile is between 2nd and 3rd values, which is 43. Similarly, the third quartile is calculated. The interquartile range is the difference between the third and first quartile. It represents the spread between the middle half of the data or the middle 50% of data. The interquartile range helps identify potential outliers. All those data points that fall outside the 1.5 times IQR below the first quartile, or 1.5 times IQR above the third quartile, are considered outliers.