why is it necessary to use a ratio estimator ratio model in cluster sampling how do you tell a ratio estimate if the model is a ratio estimator why is it important to use the ratio estimator what makes a population inverse of a ratio which model is used to estimate variance? how to estimate ratios how to use ratio estimator which is the auxiliary information of the ratio estimator? why would a population sample use a ratio estimator what is the auxiliary information of the ratio estimation model how to use ratio model how to estimate ratio of a population does a ratio estimation model have auxiliary information what is the difference between a design-based model and an inference-based model why is it necessary to use ratio estimator what is the purpose of the ratio estimator which is true about the ratio in sigma cluster sampling what model to use when estimating ratio