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PAUF 610 TA. 1 st Discussion. Population & Sample. Population includes all members of a specified group. (total collection of objects/people studied) E.g. MSPP students Sample represents only a subset of the population of interest. (some fraction of the population) E.g. PUAF 610 students.
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PAUF 610 TA 1st Discussion
Population & Sample • Population includes all members of a specified group. (total collection of objects/people studied) • E.g. MSPP students • Sample represents only a subset of the population of interest. (some fraction of the population) • E.g. PUAF 610 students
Type of Statistics • Descriptive statistics summarize numerical information. • Inferential statistics allows to draw inferences about a population based on a sample of that population.
Three main types of data • Cross-sectional data • Time-series data • Panel data
Cross-sectional data • represent measurements taken at one time across multiple subjects. • E.g. GDP for US, China, UK, Russia in 2009
Time-series data • include measurements for the same subject over a period of time. • E.g. GDP for US from 2000 to 2009.
Panel data • combine two previous types and provide measurements for multiple subjects over time. • E.g. GDP for US, China, UK, Russia from 2000 to 2009.
Constant & Variable • If a property (or characteristic) of a object stays the same it is called a constant. • E.g. hours per day • If it takes on different values it is called a variable. (A variable can take on different values for different individuals) • E.g. temperature, gender
Types of Variables • Quantitative (Numerical) • Qualitative (Categorical)
Quantitative • Numeric value that makes sense to do arithmetic operations (+, -, x, /) • E.g. height, weight, age, income
Qualitative • Records which of several groups or categories to which an individual belongs • E.g. gender, race, hair color, field of study
Measurement scales • Qualitative data (unordered or ordered discrete categories) • Nominal - numbers are used as labels for the elements in the data system; measured only in terms of whether the individual items belong to certain distinct categories (e.g. gender) • Ordinal – can be ordered on the amount of the property being measured and values are assigned in this same order.(e.g. ratings) 13
Measurement scales • Quantitative data (variables have underlying continuity) • Interval - numbers indicate rank order, and distances between them have meaning with respect to the property being measured (temperature) • Ratio – numbers have all three properties of the real-number system (order, equal distances between units and fixed origin) 14