How “free” language affects clickthrough rate
Experiment ID: #8727
Hoover Institution
Experiment Summary
Timeframe: 02/05/2018 - 03/27/2018
Hoover Institution leveraged a free eBook to grow the size of their email file. They were curious about the language used in the ads—the control ad had a call-to-action of “Get the facts on healthcare now”, but they knew from previous experiments that the word “free” was a powerful motivator. They set up a second ad with the call-to-action “Get the free eBook now” and launched an A/B test to determine a winner.
Research Question
Will adding the word “free” increase clickthrough rate?
Design
C: "Facts" language
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T1: "Free" language
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Results
| Treatment Name | Click Rate | Relative Difference | Confidence | |
|---|---|---|---|---|
| C: | "Facts" language | 0.96% | ||
| T1: | "Free" language | 0.76% | -20.7% | 100.0% |
This experiment has a required sample size of 16,665 in order to be valid. Since the experiment had a total sample size of 367,458, and the level of confidence is above 95% the experiment results are valid.
Flux Metrics Affected
The Flux Metrics analyze the three primary metrics that affect revenue (traffic, conversion rate, and average gift). This experiment produced the following results:
20.7% decrease in traffic
× 0% increase in conversion rate
× 0% increase in average gift
Key Learnings
The new ads with “free” in the call-t0-action produced a 20.7% decrease in clickthrough rate. There are at least two possible reasons for this:
- The target audience is more interested in something with perceived authority and factual basis than something that is free, possibly due to the intellectual reputation of Hoover.
- The rest of the ad copy mentions “facts”, so the “free” language might produce a break in congruency rather than a lift due to incentive.
While a valid decrease was confirmed in clickthrough rate, there was no statistically valid decrease in conversion rate, which means that additional testing is needed on the ad and landing page.