Quantiles or percentiles with XLSTAT

Dataset for Quantiles XLS113 KB

Tutorial video

  • Pro Core statistical software

  • System configuration

    • Windows:
      • Versions: 9x/Me/NT/2000/XP/Vista/Win 7
      • Excel: 97 and later
      • Processor: 32 or 64 bits
      • Hard disk: 150 Mb
    • Mac OS X:
      • OS: OS X
      • Excel: X, 2004 and 2011
      • Hard disk: 150Mb.

Benefits

  • Easy and user-friendly
    Easy and user-friendly XLSTAT is flawlessly integrated with Microsoft Excel which is the most popular spreadsheet worldwide. This integration makes it one of the simplest available tools to work with as it utilizes the same philosophy as Microsoft Excel. The program is accessible in a dedicated XLSTAT tab. The analyses are grouped into functional menus. The dialog boxes are user-friendly and setting up an analysis is straightforward.
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    Data and results shared seamlessly One of the greatest advantages of XLSTAT is the way you can share data and results seamlessly. As the results are stored in Microsoft Excel, anyone can access them. There is no need for the receiver to have an XLSTAT license or any additional viewer which makes your team-work easier and more affordable. In addition, results are easily integrable into other Microsoft Office software such as PowerPoint, so that you can create striking presentation in minutes.
  • Modular
    Modular XLSTAT is a modular product. XLSTAT-Pro is a core statistical module of XLSTAT which includes all the mainstream functionalities in statistics and multivariate analysis. More advanced features contained in add-on modules can be added for specific applications. This way you can adapt the software to your needs making the software more cost-efficient.
  • Didactic
    Didactic The results of XLSTAT are organized by analysis and are easy to navigate. Moreover useful information is provided along with the results to assist you in your interpretation.
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    Affordable XLSTAT is a complete and modular analytical solution that can suit any analytical business needs. It is very reasonably priced so that the return of your investment is almost immediate. Any XLSTAT license comes with top level support and assistance.
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  • Automatable and customizable
    Automatable and customizable Most of the statistical functions available in XLSTAT can be called directly from the Visual Basic window of Microsoft Excel. They can be modified and integrated to more code to fit to the specificity of your domain. Adding tables and plots as well as modifying existing outputs becomes easy. Furthermore, XLSTAT includes some special tools on the dialog boxes to generate automatically the VBA code in order to reproduce your analysis using the VBA editor or to simply load pre-set settings. This effortless automation of routine analysis will be a huge time saver on your part.

Quantiles and percentiles

XLSTAT has a complete tool to compute quantiles or percentiles, their associated confidence interval and graphical representations.

Quantiles are important statistical measures, they are simple to understand. The 0.5-quantile is the value such that half of the sample is below and the other half is above. It is also called the median. A quantile is called a percentile when it is based on a 0-100 scale. The 0.95-quantile is equivalent to the 95-percentile and is such that 95 % of the sample is below its value and 5 % is above.

Dataset to generate a quantile

An Excel sheet with both the data and results can be downloaded by clicking here.

The dataset has been obtained from [Lewis T. and Taylor L.R. (1967). Introduction to Experimental Ecology, New York: Academic Press, Inc]. It concerns 237 children, described by their gender and height in centimeters (1 cm = 0.4 inch).

Setting up the computation of a specific quantile

After opening XLSTAT, select the XLSTAT / Description / Quantiles, or click on the corresponding button of the "Description" toolbar (see below).

Quant1e.gif

Once you've clicked on the button, the Quantile dialog box will appear. Select the data on the Excel sheet.

In our case; the variable is the "Height". Data should be quantitative.

As the column header was selected for the variables, the Variable labels option needs to be activated.

We select the default method for estimation (weighted mean at x(Np)) and both type of confidence intervals with a 95 % confidence.

Details on statistical methods can be found in the help of XLSTAT.

Quant2e.gif

In the charts tab, we select all charts and we are interested by the 67-percentile (two third of the children are smaller and one third is taller).

Quant3e.gif

The computations begin once you have clicked on OK. The results will then be displayed.

Interpreting the results of a quantile generation

The first table displays some descriptive statistics on the height variable. The second table displays quantiles and their associated confidence interval for different commonly used values. For example, the median is 159.9 cm. The 95-percentile shows that 95 % of the children are smaller than 174.98 cm.

Quant4e.gif

The value of the 67-percentile is then displayed. Two third of the children are smaller than 164.58 cm.

The first chart (see below) allows us to visualize the empirical cumulative distribution function with the value of the 67-percentile.

Quant5e.gif

The second and third charts are a box plot and the scattergram. The 67-percentile is displayed using a blue line.

Quant6e.gifQuant7e.gif

You can also use sub-samples, for example gender can be used as a group variable. Weights associated to the observations can also be included.