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Unformatted text preview: Test of Means: ttest Some research questions are answered with rating sca/es, e.9., "How hard do you study?" notveryhard 1 2 3 4 5 veryhard or numbers, e.9,, "How old are yoL)?" Data analysis involves comparing the means across experimental conditions. o X,. mean of data in cell 1 Notation: For each cell o xt. data in cell 1 o n t: number of data points in cell 1 o L*i . sum of squares of cell 1 4 Notation Symbols . lf . total t: obt number of data points in the experiment tvalue obtained with data, which is compared to tvalue in table . critical tvalue in table, which must be exceeded to reject the null hypothesis ot ct'tl o df = Degrees of freedom: ( lf 2) I Example. adapted from T. Louie, 1999, Journal of Applied Psychology This research examines if outcome information infl uences what individuals feel they would have pred icted i n foresight. A. One group of 10 participantsread that a financial advisor purchased a company's stockestimated the stock price after one year B. Another group of 12 participantsread that a financial advisor purchased a company's stockread that the price decreased after a yearestimated what they would have thought the stock price would be after one year had they not heard the stock outcome. lndependent variable = the presumed source of differences in the data, which is often manipulated in the study. Example: The stock outcomeor price after one yearis manipurated in the study (i..e., it is provided or not provided)....
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 '09
 Louie,Therese

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