The spelling of the word "kemper" is determined by its pronunciation, which is represented in IPA phonetic transcription as /ˈkɛmpər/. The first syllable, "ke", is pronounced with a short "e" sound followed by a consonant blend of "m" and "p". The second syllable, "per", is pronounced with a short "e" sound followed by a single "p" sound and an unstressed "er" sound. The spelling "kemper" accurately reflects the phonetic properties of this word.