Cases and observations.
It is my understanding that sample size is determined by the number of individuals taking part in an experiment (from my undergrad Psychology stats course). For each individual a mean is calculated from the result of each trial. These means are entered as data in SPSS. The mantra of the stats course was “one line per each individual” in SPSS. For my current research I am consulting a professional statistician who says that power is determined by the total number of trials (observations) rather than by the number of individuals (cases). E.g. if there are 10 individuals in a study, and 80 trials per individual, there will be 800 observations, enough to conduct a multiple regression with several predictors. I am confused, since examples in books (stats for Psychology) equate sample size to number of individuals and state that the power of a test increases if more individuals are added to a sample. So, does power depend on cases or on observations? And another question (for those familiar with SPSS). Is it possible to enter the raw data (i.e. the results of every trial) instead of entering the means in SPSS? What happens with the “one line per individual” condition? Thanks!