Missing focus with Canon 50mm 1.8 lens - is it the lens or me?

I purchased a Canon EOS 650D and EF 50mm f/1.8 II lens.

Unfortunately, the auto-focus seems to miss focus at f/1.8. I've tried setting it to single-point auto-focus: it is better, but still not good enough.

This is my first DSLR, so is this likely a result my lack of skill, or perhaps is the lens at fault?

I made some tests on a target. Here is the result:

The focus is at 1cm in front of target.

Shooting parameters:

Aperture f/1.8, ISO 250m, Exposure time 1/250

Answer

1. 
   
   

   At f/1.8 the depth of field is very small - any movement (of subject or camera) between focusing and taking the shot can push the subject out of focus - so you want to take the photo as quickly as possible after focusing and don't use the "focus and recompose" technique - not at f/1.8

   
   


2. 
   

   The auto-focus on the 50mm f/1.8 is very slow, if the camera is set up to take the photo even if focus isn't locked it's possible you take pictures before the lens finished focusing - when the camera focuses it will beep and a small circle will light up in the view finder.

   
   


3. 
   

   And last - and definitely least probable - your camera or lens can be miss-calibrated (at least for each other), there are questions on this site about focus testing (like this). I believe the 650D does not have any way for you to calibrate focus and you need to take the camera and lens to a service center (or at least a good camera shop).