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One of the most common roadblocks when beginning a beta test is determining the number of testers you need. An array of different factors can impact this decision. From the number of people internally designated to support the beta project to the number of customers you have, figuring out the right number can be a headache. In reality, however, deciding how many testers you need really starts with four main factors.

In this post we’re specifically talking about private (closed) beta tests. If you’re considering running a public (open) beta test, that’s a completely different animal. Download our whitepaper on Using Public Beta Tests as a Launch Tool for more guidance.

1. The length of the test

Generally speaking, test length should be no less than two weeks and no more than twelve weeks. Of course, there are always exceptions but the number of testers can’t be defined unless you understand how long you need to keep them engaged. If you have a short window, upping the number of testers to participate in the project makes sense. More people usually means more data. With a short test window, you can add users to help make that time more productive. Conversely, a long test means managing testers for a greater period of time. If you have to string users along for months as builds roll out, you may want to consider a smaller and more effective test team that is committed to you and your product.

2. The goals of the test

The next piece is to determine what you’re trying to achieve with the beta test. Understanding the complexity of your product and what you want people to look at are both important things to consider. Fairly complex products often need more testers to test the entire scope of the product. However, even if you have the most complex product in the world, you won’t need a lot of testers if you’re only testing one new feature.

3. The costs of the test

Like anything else, beta testing has costs associated with it. Naturally, the cost difference between complex hardware prototypes and a shareware application is very different. As such, your costs could limit the number of beta testers you can have. If you can afford to spread the product around a bit, then a large number could make sense. In contrast, expensive test units often limit a beta test pool.

Some other costs to consider are shipping, incentives, and collateral materials. Each of these costs increase with the number of participants. Shipping a box for $8.50 a pop doesn’t seem too bad until you realize you have 300 beta test participants. It’s easy to identify these “per unit” costs before defining the number of users and it will help determine the potential limits based upon your budget.

4. The target market(s)

The demographics of your target market make a huge difference in who you can and can’t recruit. If your product is targeted to nuclear physicists, you have a much smaller audience to work with than a product targeted to iPad owners. Before deciding on how many people you want, you need to know who you want. Once you define that demographic, you can see what kind of pool you have to work with.

Also consider how diverse you’d like your testers to be. If you have six different personas you need to cover or a wide variety of environments you want to test, it could take a larger group to cover all your bases.

Additional Considerations

Once you have these four items defined, you can proceed by asking yourself the following questions:

How many people do I have to manage the beta test data?

The data gathered in a private beta test is directly proportional to the number of testers. So, if you have ten participants, and each turns in ten bugs, you get 100 bugs. Imagine that same scenario if you have 100 testers. You need to consider the resources you have available to deal with the data the test generates. Knowing the extent of your initial manpower to review test data will help define the amount of testers needed for your project.

Is my product connected?

In our age of the Internet, almost everything is networked. When you add the element of connectivity to a product, the game changes significantly. This means that while there may be hundreds of people separately using your product, they may all be connecting to one server. What happens if they all decide to connect at the same time? If this is a possible scenario, you might want to consider decreasing your numbers to gain some confidence about the back-end. You’ll also need to support these users as they attempt to install and connect your product, which could eat up a lot of your management manhours if your test is large.

How am I collecting the data from the test?

It’s important to consider what systems you have in place to collect and manage your feedback, as well as how time consuming they might be. The fact is, using email and spreadsheets is a very common practice in the beta world. People often don’t have systems in place to gather feedback from outside sources and instead use the tools they already have at their fingertips. The trouble with this is that beta testers love to give you feedback. Unless you have a really efficient test management tool, then you need to consider this when choosing the number of testers you want to manage.

Will I be testing over a holiday?

Remembering that beta testers are volunteers and have personal lives is an important consideration when defining test numbers. Depending on your product type, it could be a huge benefit or an utter disaster to run a test over a holiday. For entertainment products, holidays can be a great time for people to unwind and test. On the flipside, if you’re testing a business product, running a project over a holiday may result in very few suitable candidates and even less participation. If your development schedule demands that you run a beta test over a holiday, you should consider shrinking your tester team expectations due to recruitment challenges, as well as recruiting more alternates in case some of your testers leave your test to enjoy their holiday.

Once you’ve considered all these options, it’s good to sit down and come up with a figure. If you still struggle with a number, start small and then expand the number of users from there. It is always easier to add people than to cut a test short. Moreover, launching projects in stages allows you confirm your process and identify any key issues before expanding your test to the full tester pool.

Our Test Size Calculator looks at factors such as your product type, target market, your role, and your testers and does the complex test size calculations for you. Try it now to see how many testers you need for your next beta test.

P.S. If you’d like some more detailed help, we offer custom beta test plans based on your unique situation.