A researcher is interested in whether a new lotion treatment for foot odor works . she hangs out a nail salon and asks people is they have smelly feet. if they say yes, she gives them the lotion to take home, use for 3 days and return. 20 people take the lotion home . 15 return and of those 15, 10 say their feet smell good. the researchwr determines the lotion works. give 3 improvements to this experimental design (some vocabulary to consider : blocking,random assignment, placebo, double-blind , single blind etc)