stat 2300 3.1-.2

distribution shape

symmetry or skewness, peaks, clusters or gaps, outliers

outliers

unusually high or low observations

distribution center

a typical or representative data value, mean/median

distribution spread

clustered together or spread out, range, variance, standard deviation, and interquartile range

mean

xbar = sigma x / n (average)

x bar

sample mean

mu (u)

population mean

median

the middle score in a distribution; half the scores are above it and half are below it (M) if odd then middle data, if even the average two middle values, sometimes better to use median if outliers

resistant

if extreme values (very large or small) relative to the data do not affect its value substantially (median is)

mode

the most frequently occurring score(s) in a distribution (if skewed may not be in middle) good for categorical data

skewed right

mean > median

skewed left

mean < median

symmetric

mean = median , mean is preferred

median

If highly skewed use the median

range

the difference between the highest and lowest scores in a distribution, greatly changed by outliers, doesn't take into account other values

standard deviation

typical value for how far the data fall from their mean

s^2

sample variance

s

sample standard deviation

sigma

population standard deviation

sigma squared

population variance

empirical rule

68%, 95%, 99.7%