In a frequency distribution, what percent of the total number of observations lies between the first and third quartiles?

The distance between the first quartile (Q1) and the third quartile (Q3) is referred to as the interquartile range (IQR). The first quartile (Q1) or the lower quartile, is the value under which 25% of data points are found when they are arranged in increasing order. The third quartile (Q3) or upper quartile, is the value under which 75% of data points are found when arranged in increasing order. As such, the IQR encompasses the middle 50% of the data. The interquartile range give a better idea of the dispersion of data only if there are outliers .