The weights of all one hundred (100) 9th graders at a school are measured, and it is found that the mean of all the measurements is 100 lbs., with a standard deviation of 15 lbs. Explain how you would use this information to determine the percentage of students who weighed between 85 lbs and 115 lbs. Make sure your explanation includes the use of z-scores.

Question

The weights of all one hundred (100) 9th graders at a school are measured, and it is found that the mean of all the measurements is 100 lbs., with a standard deviation of 15 lbs.   Explain how you would use this information to determine the percentage of students who weighed between 85 lbs and 115 lbs.  Make sure your explanation includes the use of z-scores.

PsyDAG · Answer

Z = (score-mean)/SEm SEm = SD/√n Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability between the two Z scores.