Google Analytics sampling limitations

and how to overcome them

George  PapadongonasWeb  Analyst,  Amazee  Metrics

16/7/2013

How Google Analytics stores data

• All un!ltered data of a web property (up to 10 million hits per month) are stored in the Google Analytics database

• Each standard report has an associated data table in the Google Analytics database with unsampled data

• Reports for accounts with more than 200,000 visits per day are processed daily

• Reports for accounts with less than 200,000 visits per day are processed more often

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Google Analytics Report Sampling

• Sampling starts when the requested date range has more than 500,000 visits

• The sample size can be arranged by using the Google Analytics sampling slider. The default setting is for 250,000 visits, maximum setting is 500,000

• Visits are counted for the speci!c date range on a Web Property level, not on a Pro!le level

• Standard reports without !lters, advanced segments or secondary dimensions use always unsampled data

• Sampling applies to custom reports

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Organic Search traffic report is unsampled

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By adding a second dimension,sampling is applied

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Adjust the sampling size

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Prefer the higher precision setting

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Google Analytics Report Sampling

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How sampling is calculated

• Web property has 24,580,303 visits

• Pro!le has 492,786 visits

• Default sampling is: 250,000x492,786/24,580,303 = 5,012 visits (1%)

• Maximum sampling is: 500,000x492,786/24,580,303 = 10,024 visits (2%)

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Avoid the faster processing setting

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Prefer the higher precision setting

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Pageviews or events reports can be unreliable

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Google Analytics Report Sampling

• Visits and Visitors reports are usually reliable, even with a small sample

• E-commerce transactions, individual pageviews, adwords data, revenue and goal conversions are less reliable

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Solutions

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1. Buy Google Analytics Premium

• “Only” $150.000 / year

• 1 Billion hits processed per month

• Unsampled reports

• Data processing every 4 hours

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2. Create custom pro"les

• Instead of creating reports with speci!c advanced segments, create custom pro!les using !lters

• The default reports of all pro!les are always unsampled, even if the visitors are more than 500,000

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3. Enable Data Sampling

• Sample your data , by adding a line in the Google Analytics tracking code

code_gaq.push(['_setSampleRate', '80']); Sets

sampling rate at 80%

• Not a perfect solution, as the data are still sampled, but you have control and can avoid tracking interruption (for more than 10 million hits per month)

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4. Use smaller date range

• Break you report in smaller data ranges, each one having less than 500.000 visits

• This ensures that the data are unsampled

• Export the reports using the Google Analytics API

• Aggregate the data in Excel and create the master report

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5. Use analyticscanvas.com

• Analytics Canvas offers query partitioning, using the Google Analytics API.

• Reports are exported in smaller date ranges, so that they are unsampled and they are then merged automatically with Analytics Canvas.

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6. Download Google Analytics data locally

• It is possible to keep a local copy of Google Analytics data

• Add a line in the Google Analytics tracking code

_gaq.push(['_setLocalRemoteServerMode']);

• Add _utm.gif to your web server root

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6. Download Google Analytics data locally

86.138.209.96 www.mysite.com - [01/Oct/2007:03:34:02 +0100] "GET /__utm.gif?utmwv=1&utmt=var&utmn=

2108116629 HTTP/1.1" 200 35 "http://www.mysite.com/pageX.htm" "Mozilla/4.0 (compatible; MSIE 6.0;

Windows NT 5.1; SV1; .NET CLR 1.1.4322)" "__utma=1.117971038.1175394730.1175394730.1175394730.1;

__utmb=1; __utmc=1; __utmz=1.1175394730.1.1.utmcid=23|utmgclid=CP-Bssq-oIsCFQMrlAodeUThgA|

utmccn=(not+set)|utmcmd=(not+set)|utmctr=looking+for+site; __utmv=1.Section One"

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• Data are recorded in the server log !les

• Use http://analytics.angel!shstats.com/ to analyze them, as Urchin is discontiniued

Thanks!

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