1.3 Describing Quantitative Data with Numbers.docx - 1.3...

1.3 Describing Quantitative Data with Numbers
Mean To find the mean of a set of observations, add
their values and divide by the number of
observations
1. The mean is the “fair share” value
2. Tells us how large each observation in
the data set would be if the total were
split equally among all the
observations
1. The bar x symbol refers to the mean of a sample
a. Most of the time, the data we’ll encounter can be thought of as a sample from
some larger population
2. When we need to refer to a population mean, we’ll use the symbol (u) pronounced
“new”.
3. The mean is sensitive to the influence of extreme values
a. Because the mean cannot resist the influence of extreme observations, we say
that it is not a resistant measure of center
Median The median is the midpoint of a distribution,
the number such that half the observations
are smaller and the other half are larger
1. Arrange in order of size
2. If the n is odd, the M is the center
observation
3. If the n is even, the M is the average