FCS 504
Spring 09
Basic Statistics Terms
Population- set of data that characterizes some phenomenon
e.g. The weights of each 5-year-old in Idaho
Sample- subset of data selected from a population
e.g. The weights of 100 5-year-olds in Idaho
Statistical inference- a decision, estimate, prediction, or generalization about the population
based on information contained in a sample
e.g. Estimation of the average weight of all 5-year-olds based on the sample
Measures of Central Tendency for Quantitative Data:
Mean- is the sum of the measurements divided by the number of measurements in a data set. The
symbol is an x with a line over it.
Median- is the middle number when the measurements in a data set are arranged in ascending or
descending order.
Mode- is the measurement that occurs most frequently in the data set.
If median is less than the mean: several larger values skewed data to the right
If median equals mean: symmetrical data set
If median is greater than the mean, several smaller values skewed data to the left
Measures of Variability:
Range- the largest measurement minus the smallest measurement.
Sample Variance- for a sample of n measurements is equal to the sum of the squared distances
from the mean divided by (n-1). The symbol is s2.
Sample Standard Deviation- The positive square root of the sample variance. The symbol is s.
