Interview Questions › Root Cause Analysis

Website conversion rate (Visit -> Sign-up) has dipped slightly

The web visitor-to-signup conversion rate for your web app dipped from 12.5% to 11.1% over the past 10 days. Identify why.

Context

Total web visitors increased by 14% over the same period, but total sign-ups remained flat.

Clarifying questions to ask first

• Did the mix of traffic sources change?
• Is the conversion drop on Mobile or Desktop?

How to approach it

1. Calculate whether the dip is conversion-driven or top-of-funnel traffic mix shift
2. Segment traffic sources (High-intent Organic vs Low-intent Display/Social Ads vs Direct)
3. Examine landing page performance, page load speed, and responsive layout across devices (Mobile Web vs Desktop)
4. Evaluate recent A/B copy tests or pricing page updates

Framework: Traffic Quality Mix Shift vs True Funnel Degradation -> Device / Browser Breakdown -> Page Speed & UX Changes

Sample answer

• Traffic mix diluted by low-intent TikTok ad campaign
• Mobile web viewport bug blocking the sticky CTA button
• Page load latency increased by 1.8s due to unoptimized hero banner asset

1. Break down traffic by source: Paid Social traffic doubled with 2% conversion, diluting overall average
2. Organic conversion rate remained completely unchanged at 12.6%

Identified Simpson's Paradox: overall conversion dipped purely due to a high-volume low-intent paid social campaign; organic conversion is healthy.

What interviewers look for

• Visitor -> Sign-up %
• Traffic Quality by Channel
• Mobile vs Desktop Conversion
• LCP / Core Web Vitals