Aresearcher wants to find out the average amount of money that united states (us) adults spent on gifts during november and december of the previous year. the researcher administers the survey to 1,000 randomly selected us adults from arizona, asking the question: "how much did you spend on gifts during november and december of last year? " the data collected showed that the mean number of dollars spent per adult was $154. which characteristic of the survey could have created unreliable data?