Kiefer's main research area was the optimal design of experiments, and about half his 100 publications dealt with that topic. However he also wrote papers on a whole variety of topics in mathematical statistics including decision theory, inventory theory, stochastic approximation, queuing theory, nonparametric inference, estimation, sequential analysis, and conditional inference.
Kiefer's main research area ay ang optimal sa disenyo ng eksperimento, at tungkol sa kalahati ng kanyang 100 mga pahayagan na ang dealt sa paksa. Gayunman siya din wrote papeles sa isang buong iba't-ibang mga paksa sa matematika statistics kasama na ang desisyon teorya, imbentaryo teorya, stochastic approximation, queuing theory, nonparametric hinuha, kuru-kuro, nanggagalaing analysis, at kondisyon hinuha.