TRUSTWORTHY A/B PATTERNS: ROUNDED/SQUARE CORNERS PATTERN

Summary from the TLDR Marketing newsletter

Large-scale replications show that rounding button corners does not actually produce a large lift in clicks. The original study reported a 55% increase in clickthrough rate from rounded buttons and had a p value of 0.037, but later researchers judged the test to be underpowered. Three replication tests found effects near zero with 95% confidence intervals. A fourth pre-registered test at METRO Russia ran for 16 weeks with over 7.4 million users, and it found results below the minimum detectable effects. The combined evidence suggests the original 55% lift was likely an exaggerated result caused by low statistical power.