This is my first post. I am curious to understand that what is the effect of using non-random sample to estimate the population quantile with sample quantile? Let say, I need to measure the 10th quantile of a population. Now I have non-independent sampling points from this population (samples points are auto-correlated upto lag 4). Then, is the 10th percentile of this sample will give a good statistical estimate (in terms of unbiasedness, consistency etc.) of the population 10th percentile?
Really appreciate your thought on this regards.