The top whisker is much longer than the bottom whisker and the line is gravitating towards the bottom of the box. There are no obvious outliers in any of the samples. An attempt is made to alert you to sample values which may be unusually removed from the bulk of the data. Type 1 Inverse of empirical distribution function. The length of the box is thus the interquartile range of the sample. For a symmetric distribution, long whiskers, relative to the box length, can betray a heavy tailed population and short whiskers, a short tailed population.

Sure it makes it a little more difficult for some people For a better experience, please enable JavaScript in your browser before proceeding. You can say that you’re not sure academics actually realize the rest of the world exists but I assure you that a lot of us do. The line is close to the centre of the box and the whisker lengths are the same. On the Basic tab, select Gender and Current Salary. The elegant simplicity of the boxplot makes it ideal as a means of comparing many samples at once, in a way that would be impossible for the histogram, say. So, provided the number of points in the sample is not too small, the boxplot also gives us some idea of the “shape” of the sample, and by implication, the shape of the population from which it was drawn.

The boxplot of a sample of 20 points from a population which is skewed to the right. This is one clue that salary varies less for females than for males. The line is close to the centre of the box and the whisker lengths are the same. They are taking over the world and even forces like nationalism or ethics no longer places much restraint on their behavior.


The symmetric example above is from a Normal population. This is the era of large corporations. I assume this smaller IQR is at the root of the outlier issue I use a simple tool to assess software. Forums New posts Search forums. And that, as the original post in this thread indicates, has signficant impact on the real world. The sample quantiles can be obtained equivalently by linear interpolation between the points p[k],x[k] where x[k] is the kth order statistic.

Note that this is not unusual.

The box is much shorter for females than for males. Clustered Bar Chart with a Blx Statistic. The length of the box becomes its height.

Some work better in certain situations and others work better in other situations. Unfortunately there are more than 2 ways to do this, there are at least 7 ways to calculate these values and they lead to different results. A boxplot contains several statistical measures that we will explore after creating the visualization. The width across the page signifies nothing. Choropleth Color Map of Sums. That would be like telling all chefs to pick a single type of knife and just stick with that – why should we need a butcher knife, a butter ciircle, knives asterosk serrated edges and knives that are curved The other dimension of the box does not represent anything in particular.

The boxplot of a sample of 20 points from a ourlier with long tails.

Boxplots and Outliers

Indeed different versions of the same software change this over time. The tails are the extremities of the sample or population, rather than the centre. Avoid making definitive statements about the shape symmetry and kurtosis of your boxplots when the size of your sample i. The definitions of the yellow and red card zones are not entirely arbitrary, but not absolutely decreed either.


Type 1 Inverse of empirical distribution function. p,ot

SPSS 18 Box and Whisker Plots: Outliers | Statistics Help @ Talk Stats Forum

This example uses Employee data. If it comes from a discrete distribution then a different way might get us a better estimate.

In this example, the median is lower than the mean compare to Example: Usually they lead to similar results, but not always.

SPSS has a two stage flagging process. The asterisks or stars are extreme outliers.

Example: Boxplot

Related Topics Graphboard Examples. The length of the whiskers far exceeds the length of the box.

Boxplots of the individual samples can be lined up side by side on a common scale and the various attributes of the samples plott at a glance. I thought the software was doing something wrong.

The extra information provided by the flagging process enables you to distinguish between a truly skewed sample, and one whose apparent skewness is attributable to a single point at some remove from the rest of the data. What’s new New posts New profile posts.

They are to be interpreted as relative to a Normal population. The boxplot of a sample of 20 points from oitlier population centred on 7. It makes it a lot more difficult for about 99 percent of the population. Sample quantiles of type i are defined by: Dason Ambassador to the humans Dec 29, You have one distribution, and two totally different answers for it.