How Creating Mystery in the Subject Line can Influence Conversion Rates Experiment ID: #7576


Experiment Summary

Timeframe: 10/4/2017 - 10/9/2017

When setting up this email to promote an upcoming year-end webinar, we wondered if placing the percent difference between “#GivingTuesday” and the “last week of the calendar year” in the subject line was giving away too much too soon.

By moving the percentage to the body of the email, rather than giving away the result of our analysis in the subject line, we thought we could create more mystery and drive a greater desire to open the email.

Research Question

Will creating more mystery in the subject line result in greater opens?


C: Statistic and Date Range
T1: GivingTuesday vs Last Week


Treatment Name Conv. Rate Relative Difference Confidence
C: Statistic and Date Range 3.0%
T1: GivingTuesday vs Last Week 4.0% 35.3% 99.5%

This experiment has a required sample size of 2,347 in order to be valid. Since the experiment had a total sample size of 9,619, 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
× 35.3% increase in conversion rate
× 0% increase in average gift

Key Learnings

Not only did we see a 10% lift in open rate, but this led to a 35% increase in the amount of recipients registering for the webinar.

By creating more tension and mystery in the subject line, we gave recipients a reason to open the email and engage with the content.

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Experiment Documented by...

Nathan Hill

Nathan is an Optimization Evangelist 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.