How adding an additional newsletter opt-in checkbox affects form completion rate Experiment ID: #7469

The Heritage Foundation

Founded in 1973, The Heritage Foundation is a research and educational institution—a think tank—whose mission is to formulate and promote conservative public policies based on the principles of free enterprise, limited government, individual freedom, traditional American values, and a strong national defense.

Experiment Summary

Timeframe: 9/12/2017 - 9/19/2017

The Heritage Foundation was running an open letter to grow its email file and motivate the Senate to take action on judicial appointments. While this offer was running, they performed an analysis that found that subscribers to their Morning Bell were more likely to become donors. They decided to add a checkbox to the form to allow signers of the open letter to opt in to the Morning Bell. They hypothesized that it would decrease conversion, but the data showed that as long as the decrease was slight, the increased value of the added subscribers would more than make up for it. They launched an A/B test to determine a winner.

Research Question

Will adding an extra form field checkbox affect email acquisition rate on a petition?


C: Control
T1: With Checkbox


Treatment Name Conv. Rate Relative Difference Confidence
C: Control 64.9%
T1: With Checkbox 58.7% -9.6% 100.0%

This experiment has a required sample size of 463 in order to be valid. Since the experiment had a total sample size of 4,228, 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:

    0% increase in traffic
× 9.6% decrease in conversion rate
× 0% increase in average gift

Key Learnings

The treatment, with the additional checkbox at the end of the form, produced a 9.6% decrease in email acquisition rate. The team at Heritage decided, after analyzing the results, that this decrease was acceptable, since 63% of people who signed the treatment page also opted into the Morning Bell—which resulted in several hundred new subscribers with increased value.

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Experiment Documented by...

Jeff Giddens

Jeff is the President at NextAfter. If you have any questions about this experiment or would like additional details not discussed above, please feel free to contact them directly.