Question

A neuroscientist measures the reaction times (in seconds) during an experimental session in a sample of cocaine-addicted (n = 8), morphine-addicted (n = 12), and heroin-addicted rats (n = 6). Mean reaction times in each sample were 11, 18, and 13 seconds, respectively. What is the weighted mean for all three samples? Hint: The overall mean is not 14.0 seconds. (Round your answer to two decimal places.)

Answer 1

Answer:

14.69 seconds

Step-by-step explanation:

The weighted mean is used to calculate the mean of numbers which don't have the same "weight" or statistical relevance. In this case, that relevance is based on the sample size of each group from which the mean reaction times were obtained.

For all three samples, the weighted mean is obtaining by multiplying each one of the mean reaction times by its n value, adding them, and dividing that result by the sum of all n values.

$WM=\frac{11*8+18*12+13*6}{8+12+6} =14.69$