Introduction
Learning Outcomes
•
Be familiar with basic statistical terminology
– descriptive statistics vs. inferential statistics
– population vs. sample
– qualitative variable vs. quantitative variable
– discrete variable vs. continuous variable
•
Be able to recognize the four levels of measurement in data
– nominal
– ordinal
– interval
– ratio
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Statistics
•
What are Statistics?
– a number used to communicate a piece of information
•
What is Statistics?
– the science of collecting, organizing, presenting, analyzing, and
interpreting data to assist in making more effective decisions
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Descriptive Statistics vs. Inferential Statistics
•
Descriptive Statistics
– methods of organizing, summarizing, and presenting data in an
informative way
•
Inferential Statistics
– AKA statistical inference
– methods used to estimate a property of a population, based on a sample
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Population vs. Sample
•
Population
– the entire set of individuals or objects of interest or the measurements
obtained from all individuals or objects of interest
•
Sample
– a portion, or part, of the population of interest
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Qualitative Variable vs. Quantitative Variable
•
Qualitative Variable
– often referred to as an attribute
– the characteristic being studied is nonnumeric
•
Quantitative Variable
– the characteristic being studied is numeric
– can be ”discrete” or “continuous”
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Discrete Variable vs. Continuous Variable
•
Discrete Variable
– can assume only certain values
– there are “gaps” between the values
– result from counting
•
Continuous Variable
– can assume any value within a specific range
– result from measuring
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Levels of Measurement in Data
•
Nominal Level
– information that is represented by names or labels
– information is classified into categories and has no meaningful order
•
Ordinal Level
– information in which categories can be ordered
– unable to distinguish the magnitude of the differences between
categories
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Levels of Measurement in Data
•
Interval Level
– equal differences in the characteristic are represented by equal
differences in the measurements
– the value 0 does not represent the absence of the characteristic
•
Ratio Level
– the value 0 represents the absence of the characteristic
– the ratio between two numbers is meaningful
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