We hear a lot about “big data” these days. It can be a bit overwhelming. For everyday marketers, those without in-house data scientists, I suggest they use the KISS (Keep It Simple, Stupid) theory, and focus on the numbers that are sure to make a difference in driving revenue.

Let’s start with the email list

With lists, size doesn’t always matter. What matters is quality. You could have a 6- or 7-figure list, but if it’s made up of disengaged readers, prospects, or customers then what good is it? Aside from quality, most important is your list growth rate.

Clearly size plays a big role. After all, marketing is a numbers game. If your list or segment is extremely small, however, it could pose a problem when you’re conducting A/B tests. You’ll want a test group large enough to obtain statistically valid results.

The Email Marketing Council of the UK’s Direct Marketing Association has a handy chart that will help you determine the appropriate list size for what you’re testing. In the chart below, if your normal click rate is 10% and you want to measure if it changes by 20% (to 12% or more), you’d need a sample size of 2000 for each test cell.  That way, any click rate change of 20% or more would be a statistically significant result and not chalked up to randomness.

Deliverability rate

Obviously, this metric is key. If your emails aren’t reaching the inbox, they can’t be opened or clicked through. The best way to ensure deliverability is to have a clean list. Follow best practices and use opt in (never opt out) to build your list organically. No matter how tempting, don’t buy a list; the risks are too great.

Of course, you’ve got to follow other best practices to ensure your email ends up in the inbox, not the spam filter.  Know your own “traps” and avoid them.

Open rate

There are opens and then there are unique opens. Total opens don’t give you the total picture; it’s the unique open rate that reveals the pulse of your campaign.

Click-through rate (CTR)

The CTR isn’t just the number of clicks an email generates. It’s the number of times a link is clicked in an email, divided by the number of delivered messages. Your CTR is an important metric because it’s a gauge of how engaged your subscribers are with which content.

Conversion rate

Opens are okay, clicks are nice,  but to determine whether your campaigns are producing results, you’ve got to monitor the conversion rate. Remember, the conversion rate isn’t always about selling. It’s about prompting your subscribers and leads to take action – whether it’s to download an article, post on a social-sharing site, write a review, or whatever.

Bounces, unsubs and spam complaints

These metrics tie back to your list health. Just because we listed them last, that doesn’t negate their importance. It’s crucial you keep tabs on these stats, as a high bounce rate can damage your sender reputation with email clients and Internet service providers (ISPs).

There are two types of bounces – hard and soft – that you need to monitor. A hard bounce means an email address on your list is incorrect has expired. A soft bounce occurs when a subscriber’s email inbox is full, or when an ISP or email client rejects your message as spam. That’s why it’s important to regularly purge your list of bad email addresses.

Likewise, if you see a lot of unsubscribes you need to make sure your content is relevant. Be prepared to refine your segmentation. You also may need to reduce email frequency or give subscribers frequency options.

Lastly, you need to take spam complaints seriously. Spam complaints can lead to your company being blacklisted from the major ISPs.

The key takeaway

Focus on the metrics that mean the most in your email marketing efforts. Put your time, effort and money where it counts, and you’ll easily reap big rewards with small data.