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IT & Tech Intermediate

Mobile App Stability Metrics: Crash-Free Users, ANRs & Startup Time

Crash-free users and sessions, crashes per 1,000 sessions by version, ANR and freeze rates, p50/p90 cold start, crash-cluster Pareto, staged-rollout halt rules, regression z-tests and a stability dashboard: 8 labs on one fictional app's releases.

8 lessons 8 labs 2 h Certificate

  • One-time payment
  • 14-day money-back guarantee
  • Secure checkout with Stripe

What you'll build

What you will be able to do

Each lab ends with a concrete result that you build yourself and the checker confirms, cell by cell.

  • Turn one week of Ridgeway's daily session and user counts into crash-free sessions and crash-free users, per day and for the whole week.
  • Compare six Ridgeway releases on crashes per 1,000 sessions, flag the ones above target and find the weighted rate and the worst release.
  • Calculate the share of Ridgeway's daily users who hit an 'app not responding' freeze in each device segment, flag the bad segments and see how much the entry phones drag the overall rate.
  • Take 24 measured launches of Ridgeway, compute the p50 and p90 of cold and warm starts, the share of slow cold starts and check the p90 against the budget.
  • Rank v5.2.0's crash clusters, build the cumulative share, find how many clusters cause 80% of all crashes and draw the Pareto chart.
  • Follow the staged rollout of Ridgeway 5.2.0 day by day, apply the team's halt rule, find the day the rollout should have stopped and size the damage of going to 100%.
  • Compare the crash rate of the hotfix v5.2.1 with the previous v5.1.1, compute the difference, a two-proportion z-test and its p-value, and decide whether it is a real regression.
  • Build Ridgeway's weekly stability dashboard: count the budgets each week meets, give it a status, flag the weeks below the crash-free target and colour the at-risk rows.

About this course

Users rarely report a crash; they simply uninstall. This course teaches you to measure stability before that happens. You calculate crash-free users and crash-free sessions, then crash rate per thousand sessions for each app version. ANR and freeze rates are broken down by device segment, and cold start times are summarised as p50 and p90 percentiles. A Pareto chart finds the few crash clusters that cause most problems. You then decide whether a staged rollout should continue, wait or halt, and test whether a new version is really worse or just noisy. The final lab combines everything into a dashboard with stability budgets and red flags. For mobile developers, QA engineers and product managers.

Curriculum

Course content

8 lessons · 8 labs · 2 h · final exam

  1. Crash-Free Users & Crash-Free SessionsLab15 min4 checked tasks
    Unlocked when you buy the course
  2. Crash Rate per 1,000 Sessions by VersionLab15 min4 checked tasks
    Unlocked when you buy the course
  3. ANR & Freeze Rate by Device SegmentLab15 min4 checked tasks
    Unlocked when you buy the course
  4. Startup Time Percentiles: p50 & p90 Cold StartLab15 min4 checked tasks
    Unlocked when you buy the course
  5. Top Crash Clusters: the Pareto ChartLab15 min4 checked tasks
    Unlocked when you buy the course
  6. Staged Rollout: Continue, Wait or HaltLab15 min4 checked tasks
    Unlocked when you buy the course
  7. Regression Detection: Is the New Version Really Worse?Lab15 min4 checked tasks
    Unlocked when you buy the course
  8. The Stability Dashboard: Budgets, Status & Red FlagsLab15 min4 checked tasks
    Unlocked when you buy the course
  9. Final exam12 questions, 75% to pass, unlimited retries.

Certificate

Finish with a certificate you can verify

Complete every lesson and pass the final exam to receive a certificate of completion for this course, with a unique credential ID and a public verification page.

  • Names the course, your score and the date of issue
  • A verification link for your CV or LinkedIn profile
  • 12 questions, 75% to pass, unlimited retries.

A Tutorvo certificate confirms that you completed a course. It is not an official or professional qualification.

Illustration. Your certificate shows your own name, course and credential ID.

Before you buy

Questions about this course

Is this a subscription?

No. You pay $9.99 once for this course. There is no subscription and nothing renews automatically. Prices are in US dollars; taxes may be added where required.

What exactly do I get?

All lessons and labs of this course, the final exam and the certificate, including later updates to the course, for as long as Tutorvo offers it. Access is personal and tied to your account.

Can I get a refund?

Yes. If you are not satisfied, email hello@tutorvo.com within 14 days of buying and we refund the course in full via Stripe. The guarantee does not apply once a certificate for the course has been issued to you, or where there are signs of abuse.

When can I start?

Right after payment. Access starts immediately at your request; for consumers in the EU/EEA the statutory right of withdrawal therefore ends once access has begun, while our 14-day money-back guarantee applies regardless.

Do I need Excel or other software?

No. The labs run in a spreadsheet inside your browser on a laptop, tablet or phone. Function names and syntax follow Excel.

Is the certificate an official qualification?

No. It confirms that you completed all lessons of the course and passed its final exam. It is not an official, state-recognised or professional qualification. The name is taken from your profile when the certificate is issued.

Full details are in our Terms · hello@tutorvo.com

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