What is the best page to start optimizing?
This question comes up quite often in conversion rate optimization.

It’s an excellent question that really deserves a detailed (and lengthy) answer, but today I want to tackle a specific misconception about choosing a page that I’ve seen many people make (and even some books).

The misconception is that “It’s always better to test pages that have more traffic“.

Here’s a simple example with some numbers to explain my point.

Lets say you have an ecommerce site with these stats:

  • 10,000 visitors a month (which land on the homepage)
  • 3,000 visitors a month who reach your product detail page (the one with the add to cart button)
  • 600 visitors a month buy (convert)

This means you have a 6% conversion rate for homepage visitors and a 20% conversion rate for visitors who reach your product detail page.

All things being equal, do you start testing on your homepage or the product page?
Lets run the numbers and see.

Assuming you run a simple test with just two variations (the control/original and a single test version) and that you’ll be able to get a 15% (relative) increase in conversions from your changes, here are the results:

The control group
5,000 Homepage visitors
1,500 product page visitors
300 conversions

Testing the Homepage
Your change to the Homepage causes 15% more visitors to reach the product page which leads to 15% more conversions:
5,000 Homepage visitors
1,500 * 1.15 = 1,725 product page visitors
300 * 1.15 = 345 conversions

Using my simple Conversion Confidence Calculator it’s showing a 93% confidence level (screen shot below).

Testing the product page
Your change to the product page causes 15% more visitors to “add to cart” which leads to 15% more conversions:
5,000 Homepage visitors
1,500 product page visitors
300 * 1.15 = 345 conversions

Using my simple Conversion Confidence Calculator it’s now showing a 95% confidence level (screen shot below).

In terms of statistical significance, I’ll actually get results a bit faster testing the product page which has far less traffic than the homepage.

So, am I getting something wrong or is this a general misconception?

– Ophir