1. The Normal Distribution
Chapter 2

2. Assessing Normality A distribution is Normal IF:
Histogram creates a symmetrical, bell-shape
Box plot is roughly symmetrical
Looking at a plot of Raw Score (x) vs. Z-Score (y) (a.k.a “Normal Probability Plot”), the following is met:
Linear pattern
No systematic deviations from the line
Outliers appear as points separate from overall pattern

3. Ages of Presidents at Inauguration
Histogram is mound
shaped, but slightly
skewed right.
Boxplot is fairly sym-
metrical with one
outlier.
Normal probability plot
is basically linear with
a few gaps.
Data are approximately normal.

4. Average SAT Scores for 50 States
Histogram is some
what mound shaped
and slightly
skewed right.
Boxplot is slightly
skewed with no
outliers.
Normal probability plot
is basically linear with
a few gaps and some
slight curving on lower
half.
Data are fairly normal.

5. Number of frost days during April in Greenwich, England over a 65-year period
Histogram strongly
skewed right.
Boxplot is skewed
right with an outlier.
Normal probability plot
has gaps throughout
and a large stack of
data at 0.
Data are not normal.

6. Amount of Sodium for 54 Hotdogs
Histogram is fairly
mound shaped.
Boxplot is roughly
symmetrical.
Normal probability plot
is basically linear with
a few noticable gaps in
extreme values.
Data are approximately normal.