When researchers are studying the effect of new drug treatments on patients, bias can be introduced by
patients if they are aware of who receives the placebo.
Which type of research design eliminates this type of bias?
A researcher wants to estimate the average wholesale price of a gallon of gas in the United States. Several gas
station owners along the East Coast are asked what price they pay wholesale for a gallon of gas. The
researcher then averages these values for the sample mean price of a gallon of gas. Which problem would be
discovered if this researcher’s work were evaluated?