Test 1 Notes - 1.1 Displaying Distributions with Graphs...

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1.1 Displaying Distributions with Graphs Individuals - are the objects described by a set of data. Individuals may be people, but they may also be business firms, common stocks, or other objects. Variable - any characteristic of an individual Categorical variable - places an individual into one of several groups or categories Quantitative variable - takes numerical values for which arithmetic operations such as adding and averaging make sense. Distribution - tells what values it takes and how it takes and how often it takes these values Pareto chart - bar graph whose categories are ordered from most frequent to least frequent Outlier - an individual value that falls outside the overall pattern Time plot - variable plots each observation against the time at which it was measured Seasonal Variation - a pattern in a time series that repeats itself at known regular intervals of time Exploratory Data Analysis - uses graphs and numerical summaries to describe the variable in a data set and the relations among them 1.2 Describing Distributions with Numbers Mean -(x) average Median - (M) midpoint of a distribution Five number summary - median, the quartiles, max, and min Box plots - based on the five number summary, useful for comparing several distributions Variance and Standard Deviation - common measures of the spread about the mean as the center; standard deviation is zero when there I no spread and gets larger as the spread increases 1.3 The Normal Distributions Density Curve - is always on or above the horizontal axis and has exactly an area of 1 underneath it. It describes the overall pattern of a distribution. The mean and median are equal for symmetric density curves. The mean of a skewed curve is located farther toward the long tail than is the median The 68 - 95 - 99 .7 rule- 68% of the observations fall within standard deviation of the mean, 95% of the observations fall within 2*standard deviation of the mean, 99.7% of the observations fall within 3*standard deviation of the mean Standardized Value - z score = (X- mean)/standard deviation
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This note was uploaded on 06/24/2011 for the course STA 309 taught by Professor Gemberling during the Spring '07 term at University of Texas at Austin.

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Test 1 Notes - 1.1 Displaying Distributions with Graphs...

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