I know there are three method for wifi security. What are the relative strengths of the password encryption in WEP, WPA and WPA2 PSK?
The schemes you mention are protocols for securing 802.11x traffic over wireless networks. They don't mandate how the AP password is encrypted or hashed during storage. However, the security of the protocol does rely on making the key secure.
The short answer is that WPA2 is the only secure protocol.
But it's secure only if WPS (WiFi Protected Setup) on the access point is disabled.
For more info: How to crack a WPS enabled WiFi network
Sadly, WPS is enabled by default on the majority of WiFi Router and Access Point...