Introduction to Statistics Unit 2 Milestone
Naomi weighed 50 patients for a medical study using a scale that measures to the nearest whole pound. She then calculated the mean weight as 176 pounds, with a standard deviation
of 12 pounds.
If the distribution is normal, what percent of the data lies between 140 pounds and 212
pounds?
●
● 34%
95%
● 68%
# 99.7%
RATIONALE
Recall that if the data is normal, then the 68-
95-99.7 rule applies which states that 68% of
all data points fall within one standard
deviation of the mean, 95% of all data points
fall within two standard deviations of the
mean, and 99.7% of all data points fall within
three standard deviations of the mean.
140 pounds and 212 pounds are both 36
pounds from the mean of 176 pounds, which
is the same as three standard deviations (12
pounds * 3) in either direction. This tells us
that 99.7% of the data should lie between 140
cm to 212 cm.
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