Asked by Comet
Suppose that IQ scores have a bell-shaped distribution with a mean of 99 and a standard deviation of 12. Using the empirical rule, what percentage of IQ scores are less than 87? Please do not round your answer.
87-99 = -12/12 = -1
I get stuck here. I know 1 standard deviation lies between 68%.
87-99 = -12/12 = -1
I get stuck here. I know 1 standard deviation lies between 68%.
Answers
Answered by
PsyDAG
87 is 1 SD below mean. 68% are
±1 SD, therefore 34% are below the mean, leaving 50% - 34% = 16%
Here is another way to figure it out exactly.
Z = (score-mean)/SD
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability related to the Z score. Multiply by 100 to get percentage.
±1 SD, therefore 34% are below the mean, leaving 50% - 34% = 16%
Here is another way to figure it out exactly.
Z = (score-mean)/SD
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability related to the Z score. Multiply by 100 to get percentage.
Answered by
Summer
16%
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