Johnstone was born in Melbourne in 1956. In 1977 he graduated in mathematics at the
Australian National University, specializing in pure mathematics and statistics. Later he obtained an M.S. and a Ph.D. in statistics from
Cornell University in 1981 under
Lawrence D. Brown with the dissertation titled,
Admissible Estimation of Poisson Means, Birth–Death Processes and Discrete Dirichlet Problems. ==Research==