How can I test my oven temperature for accuracy?
Do not attempt service or replace parts of the appliance unless referred to in the owner's manual. Follow all safety precautions provided in the owner's manual.
A 250F oven temperature variation (+/-) is allowed in accordance with manufacturing standards. This variation is necessary during "cycling" to keep the oven temperature from rising excessively. This is proper operation and will not affect baking results.  
 
Oven thermometers purchased in stores do not measure oven temperature accurately. A professional digital thermometer is necessary to calibrate the oven. To check your oven temperature, try the following in-home bake test:  
  1. Prepare a boxed yellow cake mix according to package directions using 8 inch or 9 inch round cake pans.  
     
  2. Preheat the oven 15 to 20 minutes to the temperature suggested on the package directions.  
     
  3. Use a middle rack position.  
     
  4. Allow at least 2 inches between the pans and 2 inches from the pans to the oven walls.  
     
  5. Bake as directed.
 
The final product should have a smooth to slightly pebbly top crust and should be slightly rounded.