1. An image processing device for correcting pixel values of an image to reduce noise in the image, the image processing device comprising: a determination unit configured to: specify, on a normal distribution representing a noise model of the image, a reference range having a value of a target pixel as a median; compute, with respect to a local region that is an image region containing the target pixel, the number of pixels having a value falling within a first sub-range of the reference range and the number of pixels having a value falling within a second sub-range of the reference range, the first sub-range corresponding to larger values than the median and the second sub-range corresponding to smaller values than the median; correct one of the first sub-range and the second sub-range so that one of the sub-ranges in which a fewer number of pixels are distributed than in the other sub-range is narrower relative to the other sub-range; and determine a selection range that is composed of the one of the first sub-range and the second sub-range as corrected and the other one of the first sub-range and the second sub-range as is; and a generating unit configured to generate a corrected value for the target pixel by correcting values of pixels contained in a target region to reduce noise, the target region being an image region subjected to noise reduction and at least containing the local region, and the value correction involving use of values falling within the selection range from among the values of the respective pixels contained in the target region.