1.2 The Fourth and Fifth Words
After you know what you are analyzing, or, using the words of Section 1.1, after you have identified the variables from the population or sample under study, you can define theparametersandstatisticsthat your analysis will determine.
Parameter
CONCEPTA numerical measure that describes a variable (characteristic) from a population.
EXAMPLESThe percentage of all registered voters who intend to vote in the next election, the percentage of all patients who are very satisfied with the care they received, the mean time that all visitors spent on a website during a particular day.
Statistic
CONCEPTA numerical measure that describes a variable (characteristic) of a sample (part of a population).
EXAMPLESThe percentage of registered voters in a sample who intend to vote in the next election, the percentage of patients in a sample who are very satisfied with the care they received, the mean time that a sample of visitors spent on a website during a particular day.
INTERPRETATIONCalculating statistics for a sample is the most common activity because collecting population data is impractical in many actual decision-making situations.