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A neuroscientist measures the reaction times (in seconds) during an experimental session in a sample of...

A neuroscientist measures the reaction times (in seconds) during an experimental session in a sample of cocaine-addicted (n = 6),morphine-addicted (n = 12),and heroin-addicted rats (n = 8).Mean reaction times in each sample were 16, 11, and 12 seconds, respectively. What is the weighted mean for all three samples? Hint: The overall mean is not 13.0 seconds. (Round your answer to two decimal places.)

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Answer #1

as we know that weighted mean for all three samples =(n1x1+n2*x2+n3*x3)/(n1+n2+n3)

=(6*16+12*11+8*12)/(6+12+8)=12.46

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