A method to form on a substrate a first target comprising a first feature and a second target comprising a second feature, wherein the forming of the targets comprises applying the first feature and the second feature to the substrate by projection of a radiation beam through a production patterning device installed in a lithographic apparatus, the features corresponding to one or more features of the patterning device, and controlling a configuration of the lithographic apparatus to induce an aberration component, such that the first feature is applied to the substrate using a first value of an induced aberration component and the second feature is applied to the substrate using a second, different value of the induced aberration component; measuring a property of the targets; and using the measurements to determine a sensitivity of the property of the targets to changes in value of the induced aberration component.