Stats final review chapter 3
Population mean
is the sum of all the population values divided by the total number of population values.
Sample mean
is the sum of all the sample values divided by the total number of sampled values.
Median
is the midpoint of the values after they have been ordered from the minimum to the maximum.
Weighted mean
is used when there are several observations of the same value.
Geometric mean
is useful in finding the average change of percentages, ratios, indexes, or growth rates over time.
Range
is the difference between the largest and the smallest value in a data set.
Mean deviation
is the arithmetic mean of the absolute values of the deviations from the arithmetic mean.
Population variance
is the arithmetic mean of the squared deviations from the population mean.
Population standard deviation
σ is the square root of the population variance.
Sample variance
it tends to underestimate the population variance 𝜎 2. The use of (n – 1) in the denominator provides the appropriate correction for this tendency.
Sample standard deviation
is the square root of the sample variance.
Right skew or positively skewed
if there is a single peak and the values extend much further to the right of the peak than to the left of the peak. In this case, the mean is larger than the median.
Left skew or negatively skewed
if there is a single peak but the observations extend further to the left, in the negative direction than to the right. In a negatively skewed distribution, the mean is smaller than the median.