O statistics 

oblimax 

oblique factor 

observable variable 

observational error 

occupancy problems 

octiles 

odds ratio 

ogive 

omega square test 

one sided test 

one way classification 

onetailed test 

open ended classes 

open ended question 

open sequential scheme 

operating characteristic 

operational research (br.) 

operations research (am.) 

opinion poll 

opinion survey 

optimal asymptotic test 

optimal stopping rule 

optimality of design 

optimum allocation 

optimum linear predictor 

optimum statistic 

optimum stratification 

optimum test 

OrdCarver system 

order of coefficients 

order of interaction 

order of stationarity 

order statistics 

ordered alternative hypothesis 

ordered categorisation 

ordered series 

orderly stationary point process 

ordination 

organic correlation 

OrnsteinUhlenbeck process 

orthant probabilities 

orthogonal 

orthogonal arrays 

orthogonal design 

orthogonal functions 

orthogonal polynomials 

orthogonal process 

orthogonal regression 

orthogonal squares 

orthogonal tests 

orthogonal variate transformation 

orthonormal system 

oscillation 

oscillatory process 

outlier prone distribution 

outliers 

over identification 

overall estimate 

overall sampling fraction 

overdispersion 

overlap design 

overlapping sampling units 
