#WHAT IS A BOX AND WHISKER PLOT USED FOR HOW TO#

Within a narrower range of values than those in the higher range. That is, the lower scores are more concentrated Is a little right (or positively) skewed. Interquartile range, we are considering the spread of the data.ДЇor the WNBA data, the left whisker is shorter than the right. When considering the median, we are talking about the вЂњaverageвЂќ When looking at whether or not a data set is skewed (or symmetric),

We have compared three different statistical measures in this example: the The box is split evenly on either side of the median and the whiskers are Third possibility is that if, in a box plot, Quite high range, MonaвЂ™s distances were left (or negatively) skewed. Since half of MonaвЂ™s data were concentrated in a narrow but Lower values means that RamyвЂ™s distances were right (or positively) skewed. In statistical terms, the concentration of half of RamyвЂ™s data in a small range of The lower half of her distances were spread over a wider range of distances: 25% between 2 (her minimum) and

#WHAT IS A BOX AND WHISKER PLOT USED FOR HOW TO#

Let us look at some examples of how to use two box plots to compare two data sets on the same variable. Values of the data set excluding the outliers. If there is one or more outliers in a data set, for the purpose ofДrawing a box-and-whisker plot, we take the minimum and maximum to be the minimum and maximum Outliers, or extreme values in a data set, are usually indicated on a box-and-whisker plot by the 50% of theДata values lie above the median and 50% lie below the median.

The median sits within the box and represents the center of the data.

The upper whisker covers all the data values between Q3 and the maximum value,.

Q1, that is, the lowest 25% of data values.

The lower whisker covers all the data values from the minimum value up to.

The whiskers each cover 25% of the data values.

This 50% of the data lies between Q1 and Q3 and its range is the interquartile range,

The box part of a box-and-whisker plot covers the middle 50% of the values in the data set.

The horizontal axis covers all possible data values.

Internet Center for Management and Business Administration, Inc. Home | About | Privacy | Reprints | Terms of UseД¬opyright В© 2002-2010. Displaying a histogram in conjunction with the boxplot helps in this regard, and both are important tools for exploratory data analysis. They also hide many of the details of the distribution. One drawback of boxplots is that they tend to emphasize the tails of a distribution, which are the least certain points in the data set.

By using a boxplot for each categorical variable side-by-side on the same graph, one quickly can compare data sets.

Unlike many other methods of data display, boxplots show outliers.

Provide some indication of the data's symmetry and skewness.

Graphically display a variable's location and spread at a glance.

The width of the box can be varied in proportion to the log of the sample size. The expected range of the median can be shown using notches in the box. The mean and its confidence interval can be shown using a diamond shape in the box. The points outside the ends of the whiskers are outliers or suspected outliers.Д«eyond the basic information, boxplots sometimes are enhanced to convey additional information:

The ends of the vertical lines or 'whiskers' indicate the minimum and maximum data values, unless outliers are present in which case the whiskers extend to a maximum of 1.5 times the inter-quartile range. If the median line within the box is not equidistant from the hinges, then the data is skewed. The line in the box indicates the median value of the data. The range of the middle two quartiles is known as the inter-quartile range. The upper edge (hinge) of the box indicates the 75th percentile of the data set, and the lower hinge indicates the 25th percentile. The box itself contains the middle 50% of the data. The plot may be drawn either vertically as in the above diagram, or horizontally.

What is a box and whisker plot used for