Economics 10

Economics 10 - Economics 10 Introduction to Data Analysis...

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Economics 10 5/28/2008 05:25:00 PM Introduction to Data Analysis Median: Middle of the distribution Mean: Average Range: Difference between the highest and the lowest scores **SEE HANDOUT What causes variation in midterm scores?      Preparation   Beers the night before Midterm Score   Concentration   Beers “, Sleep, Health Fourty-eight percent of the people who took the exam were econ majors (or not) We possess beliefs about how the universe operates Understand physical mechanisms. Rely on these beliefs in all our activities Less of an understanding of economics mechanisms Data can be used to evaluate our model of the universe
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Evaluate casual observation with empirical analysis Data can help us understand these mechanisms What story does the data tell us? Statistics is in part the art of telling a story about numerical data Determining relationships between variables What factors determine starting salaries? Students that entered the Chicago lottery did better because they were better  students to begin with Descriptive Statistics: Numerical Methods Measuring Central Tendency o Mean, Median, Mode Measuring Variability o Range Variance, Standard Deviation Measuring Relative location o Z-score, empirical rule, etc Descriptive Stats with regard to the population is a paramater A descriptive measure of the sample is called a statistic
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Central Location: Mean, median, mode Mean takes into account all of the values  (aka = average) n x x i n 1 i = = So, if scores were 6,7,8,9,10, then xbar = (6+7+8+9+10)/5  = 8 The median of a data set is the value in the middle when the data items are  arranged in order of magnitude For an odd number of observations, the median is the middle value For an even number of observations, the median is the average of the two  middle values For the above data, the median is 8. If the data were 6,6,7,8,9, the median would be (7+8)/2 = 7.5 The Mode The mode of a set of observations is the value that occurs most frequently Set of data may have one mode (or modal class), or two or more modes o If the data has two modes, the data are bimodal
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If a distribution is symmetrical, the mean, median, and mode coincide If a distribution is asymmetrical and skewed to the left or to the right, the three  measures differ The range provides us with the distance between the smallest and the largest  observation But how do all of the observations spread out
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This note was uploaded on 10/30/2008 for the course ECON 010 taught by Professor Giummo during the Spring '08 term at Dartmouth.

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Economics 10 - Economics 10 Introduction to Data Analysis...

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