Econ 703Final Study GuideProfessor: Cathy Xue1Introduction1.1Population vs. Sample•Apopulationis simply a set of people, places, companies, things etc. that we are interested in.•Asampleis a subset of a population. You get data from this subset (or portion) of the populationto form a dataset and do analysis.•acensusis a data set that covers an entire population, not just some of the observations.1.2Descriptive Statistics vs. Statistical Inference•If we have a sample, or a census, and only want to describe the observations in that specific dataset, then the statistics we estimate are calleddescriptive statistics.•If we have a sample and want to say something about the population. This is calledinferentialstatisticsorstatistical inferenceorinference.1.3Three Levels of Data (Quantitatively)•Nominal Level Data- Can be used for classification purposes only.•Ordinal Level Data- Can be used for classification and also ranking/ordering.•Interval Level Data- This data allows us to classify, and assign rank/order, quantify distances,and perform various kinds of calculations. Interval data is always numerical.•Nominal level and ordinal level data are calledqualitative datasince we can’t do much math withthem. Interval level data is calledquantitative data. Mathematically, we can do most operationswith them.1.4Three Types of Data (Structurally)•Cross-Sectional: The data is collected at the same time and you only observe each unit once.•Time Series: You observe only one unit, but you observe it at many different points in time.•Panel Data: You observe multiple units, and you observe these units at multiple points in time.1
Econ 703 Statistics FoundationsProfessor: Cathy Xue2Tables and Graphs2.1Tables•Class Interval•Midpoint•Frequency•Relative Frequency•Cumulative Frequency2.2Graphs for Quantitative Data•Histogram•Stem and Leaf Plot•Scatter Plot2.3Graphs for Qualitative Data•Pie Chart•Bar Chart3Descriptive Statistics3.1Center of a Distribution•Mean- The average.μdenotes the population mean, ¯xdenotes the sample mean.¯x=1nni=1xi=1n(x1+x2+· · ·+xn)•Median- The middle observation when the observations are in ascending order. If there are evennumbers of observations, median is the average of the two numbers that are in the middle.