Background: Diagnostic speech recognition tests are the most direct way to quantify the distortion component of hearing loss and to evaluate the outcome of hearing prostheses. Purpose: The primary purpose of this dissertation was to evaluate the diagnostic precision of the spoken word recognition (WR) tasks that differed in listeners’ response formats (the closed- and open-set tasks). The second purpose was to improve the precision through a refined analysis of WR performance where the chance performance for listening parts (phonemes) of a word was considered. Method: WR performance for closed- and open-set tasks was obtained from seventy listeners with normal hearing. Hearing loss was simulated by presenting words in noise or in a sinewave vocoder condition. The percentage of correct phonemes in response word for each test word was computed to derive the distribution of chance performance based on an assessment of 15,000 iterations of the randomly paired response and test words. Results: Analyses found the following for the most to least precise and efficient conditions in detecting a change in hearing: open-set task scored by percent correct phonemes, open-set task score by percent correct words, 6-alternative closed-set task, and 4-alternative closed-set task. When the range of phoneme chance performance was accounted for in an open-set WR task, listeners with identical word scores were found to have different abilities to perceive phonemes. Conclusions: Closed-set WR testing has distinct advantages for implementation but its poorer precision for identifying a change in hearing than open-set WR testing must be considered. The analysis of scoring WR by phonemes on an open-set task with the estimates of chance performance reveals meaningful differences in perception that are not possible based on word scores.