The Normal Distribution Chapter 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

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.

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.

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.

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.