1. You are planning a research program and estimate it will take about 2 years to complete your study so you want to be very certain of finding the effect, if there is one. You are studying the effect of concussion on hockey players cognitive ability. Your supervisor claims that in the past 20 years the mean score on her cognitive ability test for people WITHOUT any head injury (concussion) is 64.6 (st dev = 10.3, higher numbers are better). You hypothesize that people with a head injury will perform more poorly on your cognitive test because research has consistently shown that people who play various contact sorts show cognitive decline. You run a small study with just 8 people to estimate your effect size. You find that these 8 people who have all sustained a concussion while playing hockey had a mean score of 59.8 (st dev = 11.4). If this represents an accurate estimate of the scores that hockey players achieve after a head injury, how many players would you have to include in your research to obtain a power of .90?