1 PAUF 610 TA 1 st Discussion. 2 3 Population & Sample Population includes all members of a...
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PAUF 610 TA
1st Discussion
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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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Type of Statistics
• Descriptive statistics summarize numerical information.
• Inferential statistics allows to draw inferences about a population based on a sample of that population.
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Three main types of data
• Cross-sectional data
• Time-series data
• Panel data
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Cross-sectional data• represent measurements taken at one
time across multiple subjects.• E.g. GDP for US, China, UK, Russia in
2009
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Time-series data• include measurements for the same
subject over a period of time.• E.g. GDP for US from 2000 to 2009.
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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.
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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
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Types of Variables
• Quantitative (Numerical)
• Qualitative (Categorical)
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Quantitative
• Numeric value that makes sense to do arithmetic operations (+, -, x, /) – E.g. height, weight, age, income
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Qualitative
• Records which of several groups or categories to which an individual belongs– E.g. gender, race, hair color, field of study
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Measurement scales
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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)
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Measurement scales
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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)
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intervalcontinuous
numerical proportiondiscrete
datadichotomous
nominalnon-dichotomous
categoricalordinal
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