You are testing to see whether there is a difference between how much people spend on food when they're out if they are alone versus if they are with their friends. You want to collect information on the amount of money spent per meal at a particular restaurant for two different groups; for your first sample (represented using number 1), your sample contains 36 meals served to individuals sitting by themselves. For your second sample (represented using number 2), your sample contains 69 meals served to individuals sitting with at least another person. You hypothesize that people tend to spend more on food when they are with company than when they are alone. In other words, you have the alternative hypothesis HA : M1 - /2