Perfect999 said:
Can a pc and iPad in the same house cause the wifi speed to decrease?
Yes, that is entirely possible.
However, there are various factors to consider. When you say wifi speed, do you mean local transfer speed, I.e. file transfer from a PC to wireless hard drive, or the Internet speed?
Anyhow, when both the PC and iPad are connected to the Internet and actively download stuff, then yes, the Internet connection may be the limiting factor and thus reduce download speed for either device, as the Internet connection gets shared. This is more likely to occur with a slow internet connection. For me, the fiber-optics connection is faster then the iPad's wifi connection, so it is not really an issue.
Overall, if you are just browsing the web, you won't notice much slowdown on either device.
The other question is, what wifi router you use.
Somehow incomplete answer, my brain is already asleep at 1am
Anyway, usually you shouldn't notice much slowdown, unless you download movies, etc. then the Internet on the other device will be slightly slower.