Use the empirical rule to determine the approximate probability that a z value is between 0 and 1 on the standard normal curve.

1 Answer
MeneerNask · henriquepizarro
Feb 20, 2015

You need to use a table of standar normal distribution curve. There are different kind of tables (cumulative, fi function, stc..), but your anwer is:
#P( 0 < z < 1) = 0.34#

The empirical rule allows you to make a quick assessment of probability without using a table. Just memorise these three numbers:

#0.34=34%# is less than one standard deviation #sigma# higher than the mean #mu#
#0.135=13.5# is between #sigma# and #2sigma# higher than #mu#
#0.025=2.5%# is more than #2sigma# higher than #mu#

The same goes for values below #mu#, as the normal curve is symmetrical. (So you have 68% of your values between #mu-sigma# and #mu+sigma#, or between #z=-1# and #z=+1#)

Remember every #sigma# translates to #1# on the #z#-scale

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