What is n-gram analysis?

N-gram is a methodology used by PPC marketers that groups up the search term report by individual words, pairs, or trios of words to identify themes of what’s performing particularly well, or particularly poorly.

For example, the search terms “free cinema tickets” ,“free cinema popcorn”, and “free cinema locations” all contain the 1-gram “free”, as well as the 2-gram “free cinema”.

Given the length of most search term reports it isn’t possible to perform an n-gram analysis simply by reading through the search term report and splitting out the themes. It’s also very time-consuming to perform this analysis in Excel. We need to download the search term report, split the search terms into individual words, then group each term by word. We then need to split the search term into pairs, or trios, of words, and group by those phrases too.

Adding n-gram negative keywords in Opteo

This Improvement sifts through the search term report to find single, pairs, or triplets of words that perform poorly and should be added as a negative keyword. To do so, our algorithm first gathers the relevant data, and then analyses performance to determine if a particular word or phrase should be added as a negative.

Data gathering

When sifting through the search term report Opteo first filters out any irrelevant words. Our algorithm:

  • Ignores any stop words such as “and”, “in”, or “the”. We also analyse the language of the search terms to be sure to filter stop words in any language.

  • Filters out any search terms that have already been covered by a new negative in the account. For example, if Opteo is analysing performance from the previous 180-days, but a particular word was added as a negative only 90-days ago, Opteo won’t then look at any search terms from the first 90 days worth of data that contain that particular word.

  • Doesn’t consider any search terms that haven’t had a click yet, because they haven’t spent any money yet Opteo doesn’t treat these as a priority.

To make sure we’re looking at a combination of the freshest data, but with enough volume to be able to make a decision, Opteo will:

  • Perform a ‘Minimum Clicks’ calculation which looks at on average, for this keyword and keywords like it, how many clicks does it take to get to 3 conversions (minClicks = (1/AvgConvRate)*X). For example, if a group of campaigns has an average conversion rate of 10%, then minClicks = 30 clicks.

  • Check multiple look back windows of 30, 90, and 180 days. In our example above if a campaign has achieved 30 clicks within the last 30 days, Opteo will perform an n-gram analysis looking at this most recent data only. However, if we’re not able to get enough volume looking only at the last 30-days, then Opteo will check the last 90 and then the last 180 days as well.

Finally, before recommending an n-gram negative, Opteo will check the percentage of the cost of all search terms that contain the n-gram. If it’s above 10% we won’t recommend adding that n-gram as a negative because it can be dangerous to reduce the volume in the account so severely.

Analysing n-gram performance

Once Opteo has identified n-grams from the search term report, it then analyses the performance of the entire campaign group, comparing the n-gram’s performance to the average (or target) of its Campaign Group.

If the n-gram has 0 conversions, and its cost is three times more than the average or target CPA, Opteo will recommend adding it as a negative keyword.

Note: If you are directly targeting the n-gram, Opteo will instead recommend reducing its bid instead as part of the separate Improvement: Reduce N-Gram Bids

Using the n-gram negative improvement in Opteo

When Opteo generates an Add N-Gram Negative Improvement it will present you with all the relevant data to help you decide if you’d like to push it live to your Google Ads account. Opteo shows you:

  • How the n-gram performs compared to the average (or target if you’ve set one) of the Campaign Group

  • The search terms which contained the n-gram. Here you may notice that the total cost and conversions of the keyword is smaller than that of the n-gram. This is because Opteo shows the sum cost of the keywords that specifically contain the n-gram, whereas the search terms that contain the n-gram might have triggered other keywords as well.

There are a few actions you can take before pushing this Improvement live to Google Ads.

First, you can modify the n-gram if you’d like. For example if Opteo recommends adding the negative keyword “free cinema” you modify this to either just “free” or “cinema”.

As a fail-safe, Opteo will check you’re not going to add any negatives that will reduce conversions. For example, if the word “cinema” has brought you conversions in the past, Opteo will warn you before you add it as a negative.

Second, you can choose which shared negative list to add the negative keyword to. Or, you can also add it to a group of campaigns too.


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