the central 80% of the Z table lies within µ ± 1.282σ
So, plug in your numbers
You can play around with Z table stuff at this excellent site:
http://davidmlane.com/hyperstat/z_table.html
assume that blood pressure readings are normally distributed with a mean of 111 and standard deviation of 7. A researcher wishes to select people for a study but wants to exclude the top and bottom 10 percent. What would be the upper and lower readings to qualify people to participate in the study?
1 answer