TornadoGuard
TornadoGuard
[The comic is a single panel which resembles a reviews page for a mobile phone application. Next to the app title is a pictogram of a tornado touching the ground]
----App store---- TornadoGuard From DroidCoder2187 ----------------- Plays a loud alert sound when there is a tornado warning for your area. ----------------- Rating: ★★★★☆ Based on 4 reviews ----------------- User Reviews: [The first three reviews show five black stars. The last review shows one black and four white stars.] Reviewer 1 (Dark silhouette): ★★★★★ Good UI! Many alert choices. Reviewer 2 (Helicopter without rotors): ★★★★★ Running great, no crashes Reviewer 3 (White square with black triangles at the top left and bottom right corner): ★★★★★ I like how you can set multiple locations Reviewer 4 (White car): ★☆☆☆☆ App did not warn me about tornado.
[Caption below the comic:] The problem with averaging star ratings

This is a comic with a take on an application store - the most common app stores are for iPhones and Android devices. App stores take all the reviews and average the ratings for the overall star rating.
In this comic, we see why this is sometimes a bad idea, especially with something as important as an app called TornadoGuard that should alert the user if there is a tornado warning for an area, an announcement indicating that a tornado is approaching. In this case, there are three 5 star reviews about the stability and user interface features of the app, left by users who actually never experienced its core functionality (simply because they never used it in a place where there was a tornado since they got it); however, the only review related to whether the app really works is given the same weight as the others, and sadly for that user, the TornadoGuard app failed in alerting the user to an upcoming tornado. Tornadoes are a recurring subject on xkcd. Also see future comic 1098: Star Ratings , 1754: Tornado Safety Tips .
In 2615: Welcome Back Cueball returns to the app after almost 11 years to find that he has to walk through all kinds of info before getting to know if the visible tornado is likely to head his way...
The title text is software-developer humor, the same as used in 583: CNR which contains further explanation. It is a note from the developer's bug report , which said they could not reproduce the error. Of course, they could only reproduce such a failure if there were a tornado coming towards their area, and if a tornado warning was issued. This is a fairly rare situation, especially in certain areas of the world. This lack of suitable testing conditions explains why the actual alert portion of their code appears to be faulty.
This is a common problem with code that cannot be easily tested -- that when finally needed, it does not actually work.  This is the reason for emergency drills.
In 2219: Earthquake Early Warnings an app for warning of Earthquakes was the main topic, but tornado warnings was mentioned in the title text.
In 2236: Is it Christmas? being right most of the time, except when it matters was the topic.
[The comic is a single panel which resembles a reviews page for a mobile phone application. Next to the app title is a pictogram of a tornado touching the ground]
----App store---- TornadoGuard From DroidCoder2187 ----------------- Plays a loud alert sound when there is a tornado warning for your area. ----------------- Rating: ★★★★☆ Based on 4 reviews ----------------- User Reviews: [The first three reviews show five black stars. The last review shows one black and four white stars.] Reviewer 1 (Dark silhouette): ★★★★★ Good UI! Many alert choices. Reviewer 2 (Helicopter without rotors): ★★★★★ Running great, no crashes Reviewer 3 (White square with black triangles at the top left and bottom right corner): ★★★★★ I like how you can set multiple locations Reviewer 4 (White car): ★☆☆☆☆ App did not warn me about tornado.
[Caption below the comic:] The problem with averaging star ratings
