Descriptive statistics

Descriptive statistics

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  Descriptive Statistics By AttaullahKhan And Sadia Saleem
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  Terms of Statistics Refers tomethods and techniques used for describing, organizing, analyzing, and interpreting numerical data. Statistics is often categorized into descriptive and inferential statistics.
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  Types of statistics: •Descriptive (which summarize some characteristic of a sample) • Measures of central tendency • Measures of distribution • Measures of skewness • Inferential (which test for significant differences between groups and/or significant relationships among variables within the sample • t-ratio, chi-square, beta-value
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  Univariate Analysis • Univariate analysisinvolves the examination across cases of one variable at a time. There are three major characteristics of a single variable that we tend to look at: • the distribution • the central tendency • the dispersion In most situations, we would describe all three of these characteristics for each of the variables in our study.
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  100,000 fifth-grade students takean English achievement test Researcher randomly samples 1,000 students scores Used to describe the sample Based on descriptive statistics to estimate scores of the entire population o 100,000 students
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  Descriptive Statistics Thus, descriptive statisticsare used to classify, organize, and summarize numerical data about a particular group of observations. There is no attempt to generalize these statistics, which describe only one group, to other samples or population.
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  Descriptive Statistics: Methods of describingthe characteristics of a data set. Useful because they allow you to make sense of the data. Helps exploring and making conclusions about the data in order to make rational decisions. Includes calculating things such as the average of the data, its spread and the shape it produces.
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  Continue In other words,descriptive statistics are used to summarize, organize, and reduce large numbers of observations. Descriptive statistics portray and focus on what is with respect to the sample data, for example: What percentage of students want to go to college?
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  Types of Descriptive Statistics Data Distribution Percentageand Graphs Summarize Data Central Tendency and Variation
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  Data Distribution Tables Frequency Distributions Relative Frequency Distributions
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  • A frequencydistribution is a table that shows classes or intervals of data with a count of the number in each class. The frequency f of a class is the number of data points in the class. Frequencies Upper Class Limits
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  Cont. • Graphs • Pieor Bar Chart or Histogram • Stem and Leaf Plot • Frequency Polygon
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  Graphs A pie chartis a circle that is divided into sectors that represent categories. The area of each sector is proportional to the frequency of each category.
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  Summarizing the Data Central Tendency(or Groups’ “Middle Values”) Mean, Median, Mode Variation (or Summary of Differences Within Groups) Range Interquartile Range Variance Standard Deviation