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An important consideration when designing a

study is the way you assign your conditions. 

In on study of the impacts of certain kinds of seating in restaurants, some of the locations of a restaurant chain were assigned to a

condition that received new outdoor seating, while other locations did

not.  To determine which locations

actually got the new seating, the restaurant owner flipped a coin for each

location, and when the coin came up ‘heads’ that location received the new

seating, but when the coin came up ‘tails’ that location did not receive the

new seating.  By using this procedure,

the owner could be reasonably confident in the assumption that the restaurants

in the two conditions would vary similarly in size, age of facility, available

outdoor space, etc.  This assumption is a

safe one b