The sample size you need depends on the size of the overall campaign population. For 10,000 customers, as in the example above, 5% is sufficient. As a rule of thumb, smaller campaigns require a larger percentage to generate a valid control group. So, for campaigns targeting less than a couple of thousand customers, it's a good idea to use 10%-20% instead.

Raising general selling activity to increase results seems logical. Raise the level of effort to put more into the top end of the funnel, and more business should result at the bottom, right? But this model of sales productivity is based on a flawed assumption: that if you just raise the amount of prospecting activity, youll find enough leads to fill your pipeline, and therefore achieve the goal.