In an experiment, evaluate the validity of the steps leading up to the conclusion for it to be valid. Random and systematic errors can contribute to the uncertainty of a measurement.

Accurate results are free from systematic and random errors and accuracy also involves trueness and precision. Precision is defined as the closeness of agreement between individual values.

Systematic random sampling controls the distribution of the sample by spreading it throughout the sampling frame or stratum at equal intervals, thus providing implicit stratification. You can use the ...

W. G. Cochran, Relative Accuracy of Systematic and Stratified Random Samples for a Certain Class of Populations, The Annals of Mathematical Statistics, Vol. 17, No. 2 (Jun., 1946), pp. 164-177 ...