Wifi
Wifi
[A line graph with a curve that starts just right of the Y-axis above the middle of the axis. Then it increases slightly and stays almost stable on a long flat plateau before it falls off fast towards the right.  Each axis ends in an arrow and has a label to the left of the Y-axis and below the x-axis. Over the curve there are three labels, pointing with one arrow to the two rising and falling parts, and three arrows to the center label above the plateau.] Y-axis: Probability houseguest will be able to connect to WiFi X-axis: Houseguest tech-savviness Left label: Can't find wifi settings Center label: Works fine Right label: Something involving the word "firmware"

This comic shows the supposed probability that a guest will be able to connect to the owner's Wi-Fi in graph form. Connecting to a new Wi-Fi network is a fairly simple operation that most people can perform, typically only requiring selecting the correct network name on a settings screen, then entering a password.
The graph starts with tech-illiterate people who don't even know how to control their Wi-Fi connection ("can't find wifi settings"). This group has slightly lower than normal probability of connecting successfully, since they would not know what to do if left alone. However, they still have a reasonable chance to connect as long as someone is available to help them. Once the initial setup is done, they can continue using the connection without any technical knowledge or intervention.
The average case in the middle of the graph represents typical users who simply wish to connect and gain Internet access ("works fine"). This group of users have enough knowledge to be able to connect and are then satisfied with the connection just working. Since networking devices use a standard protocol to communicate behind the scenes, users typically will not experience any issues.
Finally, the large drop in the graph on the right-hand side is explained by "something involving the word 'firmware'". Firmware is programming which operates a device at the lowest level, typically stored in a ROM or an EEPROM/flash. Both Wi-Fi routers and guest's devices (smartphones, tablets, computers) have firmware. Modifying the firmware can have certain benefits, for example to gain features that aren't included in the base product. Also, especially for newly adopted wireless standards (such as, most recently, IEEE 802.11ac ), incompatible interpretations of the standard may prevent devices from different manufacturers from communicating reliably or at full speed, requiring firmware changes to patch the issues. However, working with firmware requires a great deal of technical knowledge, and can be quite risky for people without experience. Not all custom firmware will interoperate correctly with all devices. Technical issues with custom firmware can also be harder to fix due to lack of support from the device manufacturer. In the worst case, installing the wrong firmware, or any errors or glitches in the process, can even leave devices bricked . It's likely that the sharp dropoff in the graph is caused by inexperienced users who know "just enough" to want to modify their firmware, but don't know how to deal with the multitude of issues that can arise. Particularly for users whose connection was already working fine but nevertheless want to experiment with new firmware, their changes often end up worsening their chances of connecting.
The title text indicates that the curve recovers once users are more experienced, and can consistently install firmware correctly to get a working connection. In such case, the users are able to enjoy better connections through their firmware changes while avoiding their pitfalls. These experienced users are often able to diagnose and fix connection issues through the appropriate use of firmware, making their chances of connecting even better than the average user.
Randall has previously used the title text to add extra info that would not fit in the main graph.  This has happened in 388: Fuck Grapefruit , 1242: Scary Names , 2466: In Your Classroom and 1501: Mysteries . The first three have extra data points mentioned there because they are far off the chart, whereas the last has a point whose description would be too long to fit on the chart. All these other graphs are scatter plots, as opposed to this comic being a line-graph.
Computer issues have previously appeared in several xkcd comics, notably 456: Cautionary , where WiFi problems specifically are mentioned in the title text.
The apparent paradox of people knowing more about a subject also having more problems with it is also explored in 1760: TV Problems .
[A line graph with a curve that starts just right of the Y-axis above the middle of the axis. Then it increases slightly and stays almost stable on a long flat plateau before it falls off fast towards the right.  Each axis ends in an arrow and has a label to the left of the Y-axis and below the x-axis. Over the curve there are three labels, pointing with one arrow to the two rising and falling parts, and three arrows to the center label above the plateau.] Y-axis: Probability houseguest will be able to connect to WiFi X-axis: Houseguest tech-savviness Left label: Can't find wifi settings Center label: Works fine Right label: Something involving the word "firmware"
