You Ask, I Answer: Sample Sizes for Web Analytics?

Courtney asks, “How many web sessions (or users) would you need to send to a website for the results to be significant?”

At first, I thought this question was about A/B testing, which has a whole range of statistics for it. But Courtney is actually asking about how many visitors you need for web analytics to be useful in general. There are two components here – first, what is your website’s obtainable market, and second, how much time are we talking about? Web analytics data gets more representative of your obtainable market as your marketing gets better.

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In today’s episode Courtney asks how many web sessions or users would you need to send to a website for the results to be significant? It’s interesting At first, I thought this question was about AV testing, which is most of the time where we start getting into discussions about statistics, statistical significance when it comes to your analytics, but they’re actually asking about how many visitors you need for your web analytics to be useful in general.

And there’s a few different answers for this.

First, if you’re just getting started or you’re just trying to get a sense of your website’s performance, then it’s really only a question of time you need most of the time, a minimum of 30 days of traffic data to collect anything useful with web analytics, more you have the better.

90 days is better.

Yours is obviously better because you can do year over year Parson’s.

That’s especially true if your business has a high level of seasonality to have cyclicality to it.

So that time part is is probably the most important important part.

When it comes to measuring your website.

The number one thing to measure is improvement against yourself.

Right? There’s that’s really the the best way to judge Are you getting better results? Are you getting, you know, even 1% more conversion this month than you were getting last month you’re getting 1% more traffic from qualified sources this month and last month, that kind of measurement is is the best because it takes away all the external factors and focuses only on what you’re doing to grow your website.

Now, if we want to get fancy one way to think about your web analytics is how Much of your obtainable market are you getting this is the market that you could be getting of people in your space.

So your website should be attracting more of your obtainable market as more time goes on as your marketing gets better as your search engine optimization gets better, and so on and so forth.

So what is your obtainable market for a website? For most websites, this is going to be a tiny piece, a tiny, tiny little sliver wafer thin of what your audience is searching for it in your SEO topics.

So say, digital marketing analytics, how many people search for that? test? It’s a 10 million people, right? What’s the likelihood that you could obtain any of that through SEO, assuming you’re really good at it, you’re still talking like probably like a 10th of 1% So it’s a tiny little slice.

So it’s going to be a very, very thin slice of that obtainable market.

Once you’ve figured out what is obtainable, what’s what’s you’re likely to be able to attract.

I use, I typically use a benchmark of cost per click for that.

If you’re if you’re a company and you take all your major topics, and you add up the cost per click, and you add up the number of clicks, and you get this out of almost any SEO tool, and you will see its costs $27 million a month to capture 100% of the traffic great, what percentage of budget Are you willing to throw into that? Right, if you got like, just saying, well, I got 100 bucks a month I could spend on on on paid search.

Oh, great.

So to add that 27 million, your hundred bucks is is the percentage you’re committed to obtaining.

Now, I’m not saying go out and spend that I’m saying that’s a good way to just kind of get I feel a sense of benchmark of what percentage of the attainable market you’re likely to get, because that’s how much you willing to commit in terms of resources.

do add in the time spent as money for organic SEO for content marketing, because that is an important part of trying to obtain that audience.

So that’s part one.

Part two is then you need to calculate a sample size.

Right? What sample size, assuming you can get a representative portion of that overall audience that’s searching for the things that you do.

What sample size Are you comfortable with? That would tell you yes, I’m getting enough of the audience that I can.

I should be getting, you know, a good idea of what people are interested in for the purpose of analyzing that audience in your web analytics.

most marketers most of the time, cuz we’re not doing anything life saving right? This is not the ER are comfortable with a confidence level of 95% Confidence Interval plus or minus 3%.

What that means is confidence level in statistics is, if you repeated this test 100 times 95% of the time, if you have a 95% confidence level, you will get the same results, right? If you were doing something with like pharmaceutical trials, you want to competence level like 99% of the time or 99.9 or point 999, you want to crank that number up so that you get reliable results from marketing where no one’s going to die 95% hence, just fine confidence interval says that when you repeat that test over and over again, your results should be plus or minus whatever that number is.

In this every time you repeat it, so a plus or minus 3% says that result should have an a margin of error roughly a plus or minus 3%.

So, if you’re reading that test over and over and over again, you should not very much more than that number outside, the higher you crank up The confidence level and the lower you crank the confidence interval but larger sample size you need.

The first time somebody does that statistical test, I’ll crank those numbers like to do the extremes of like, Oh, you need 100% of your sample of your audience to to get reliable sample like, Oh, that’s not helpful.

plug those numbers plus your obtainable market into the survey sample tool of your choice, you’ll get the required sample size for any kind of survey.

So you know, for say, 10,000 people with 95% confidence level and plus or minus 3% confidence interval, you’re talking 964 people, right? That’s, in fact, what Courtney was asking about.

That, again, that’s only useful if you’re trying to figure out, you know, how much of the audience Do I need to have as traffic on my website to do statistically relevant judgment about them, their age, their demographics, their behaviors, their search terms and things like that, for the purposes of managing your market.

You don’t need that at all.

You don’t need that at all.

All you need to focus on is your numbers for awareness, consideration, evaluation and conversion.

And are you improving them? Day after day, week over week, month over month, year over year if you’re if you are improving, that’s all that really matters.

And I would say that is true for your Google Analytics, your web analytics, your marketing, automation, your email marketing, your social media metrics, any metric at all that you’re measuring.

Focus on the improvement focus on what can I do to get the improvement A number of years ago, Julian Smith, the CEO of breather, said, when you want to go into growth mode for a startup, the number one thing you can do is pick one relevant metric and come hell or high water, make it grow 8% week over week, he’s like that.

If you want to grow and you’re willing to throw time you want to throw energy you Going through all your money at this at something to make your business grow, pick one thing that’s relevant and force that thing to grow 8% week over week and it will have a spillover effects into everything else.

So that’s an interesting way to think about it.

Now you may not be able to get 8% a week, but could you get 5% month over month? Something to think about? Great question, Courtney complicated question.

There’s a lot of statistical stuff to dig in here.

And it really shows that even something as simple as a simple question, a seemingly simple question about web analytics can have a lot of stats and data science behind it in order to really dig into what it is you’re after.

So good question, complicated question more complicated than you thought.

As always, please leave your comments below.

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