Tips, take 2. In another experiment to see if getting candy after a meal would induce customers to leave a bigger tip, a waitress randomly decided what to do with 80 dining parties. Some parties received no candy, some just one piece, and some two pieces. Others initially got just one piece of candy, and then the waitress suggested that they take another piece. She recorded the tips received, finding that, in general, the more candy, the higher the tip, but the highest tips (23%) came from the parties who got one piece and then were offered more. (Source: Sweetening the Till: The Use of Candy to Increase Restaurant Tipping. Journal of Applied Social Psychology 32, no. 2 [2002]: 300309) a) Diagram this experiment. b) How many factors are there? How many levels? c) How many treatments are there? d) What is the response variable? e) Did this experiment involve blinding? Double-blinding? f) In what way might the waitress, perhaps unintentionally, have biased the results?

STAT 2004 CHAPTER ONE: WEEK 4 SAMPLE STATISTICS n 2 1 2 Sample variance- s = n−1 i=1x ix´) Sample standard deviation- Tells you how spread out your data is. It is the square root of the variance. QUANTILES Also known as percentiles. o If you are in the 70 percentile, you are better than 70% of your class and not as good as 30%. DISTRIBUTION Describes shape, center, and spread/variation of data. For the images below, imagine histograms that fit the depicted curves. BOXPLOT A boxplot uses a five number summary consisting of the median (Q ), 2