First, check the thermostat sensor bulb at the back of the oven. It should look something like this:Make sure that this rod is secure and not touching the oven walls at all. This is something that could throw off the temperature reading. If it is touching, see if you can tighten the vises holding the bulb or otherwise position the bulb away from the wall, or call a repair person. Then check the oven temperature before proceeding.
Next, remove the oven temperature knob and take a look at the back. If it looks like this:All you have to do is loosen those two screws and move the dial clockwise or counterclockwise to shift the numbers. For our oven, one tick on the dial seemed about equal to 50°. Tighten the screws back up and turn on the oven to see if everything matches.
If your knob doesn't look like this, then the alignment mechanism is probably in the shaft of the knob. Use a screwdriver and turn it clock-wise if your oven is running hot (to lower the temperature) or turn it counter-clockwise if your oven is running cool (to raise the temperature).
Again, this fix isn't actually adjusting the temperature sensor or any of the oven's heating mechanisms. Call a repair person if you think something is off with either of those things.
Related: Our Adventures in Oven Cleaning
(Images: Emma Christensen for the Kitchn)