They are a simple measure of the spread of the data, which is not affected by extreme values.
The interquartile range can be more useful when the first and fourth quartiles contain very little data, in other words there are only a very few high or low data points.
It is a simple but crude measure of the spread of data.
Outliers
Quartiles.
Quartiles are values that divide a sample of data into four groups containing the same number of observations. You will find details in the related link.
There are 5 quartiles in any data set.
The interquartile range can be more useful when the first and fourth quartiles contain very little data, in other words there are only a very few high or low data points.
It is a simple but crude measure of the spread of data.
Probably the box and whiskers plot, but there are others.
quartiles
Outliers
Quartiles.
Definately more than 4 pieces of data (intuitively, otherwise at least 2 of your quartiles will fall in exactly the same place as each other). But I think that's the only limit on how much data you need - there is no upper limit.
Quartiles are values that divide a sample of data into four groups containing the same number of observations. You will find details in the related link.
A Box and Whisker Plot
a graphic way to display the median, quartiles, and extremes of a data set on a number line to show the distribution of the data.
A lower quartile i s the mediaon of the lower half of a data set. A data set is divided up into different quartiles.