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Data and Statistics

Data and Statistics. Chapter 1 BA 201 – Fall 2010. Statistics. Numerical facts such as averages, medians, percents, and index numbers. Art and science of collecting, analyzing, presenting, and interpreting data. . Data and Data Sets.

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Data and Statistics

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  1. Data and Statistics Chapter 1 BA 201 – Fall 2010

  2. Statistics • Numerical facts such as averages, medians, percents, and index numbers. • Art and science of collecting, analyzing, presenting, and interpreting data.

  3. Data and Data Sets • Data are the facts and figures collected, analyzed, and summarized for presentation and interpretation. • The data set is all the data collected in a particular study.

  4. Elements, Variables, and Observations • Elements are the entities on which data are collected. • A variable is a characteristic of interest for the elements. • An observation is the set of measurements obtained for a particular element.

  5. Data Sets, Elements, Variables, and Observations Variables Observation Elements Stock Annual Earn/ Exchange Sales($M) Share($) NQ 73.10 0.86 N 74.00 1.67 N 365.70 0.86 NQ 111.40 0.33 N 17.60 0.13 Dataram EnergySouth Keystone LandCare Psychemedics N 74.00 1.67 Data Set

  6. Scales of Measurement Nominal Ordinal Interval Ratio

  7. Scales of Measurement • Nominal – labels or names. • E.g., CoB, CoST, CoAL, CoH; male or female; department 1, 2, 3, 4, … • Ordinal - have the properties of nominal data and the order or rank of the data is meaningful. • E.g., Freshman, Sophomore, Junior, or Senior

  8. Scales of Measurement • Interval – have the properties of ordinal data, and the interval between observations is expressed in terms of a fixed unit of measure. • E.g., ACT score of 23, 24, 25, …; years. • Numeric • Ratio - have all the properties of interval data and the ratio of two values is meaningful. • E.g., 30 credit hours versus 120 credit hours • Must include zero

  9. What You Can Do With Scales http://www.graphpad.com/faq/viewfaq.cfm?faq=1089

  10. Categorical or Quantitative Data Categorical (or Qualitative) Quantitative How much or how many Numeric Interval or ratio More statistical tests available • Grouped by categories • Numeric or non-numeric • Nominal or ordinal

  11. Scales of Measurement Data Categorical Quantitative Numeric Numeric Non-numeric Nominal Ordinal Nominal Ordinal Interval Ratio

  12. Cross-Sectional or Time Series Data • Cross-sectional data are collected at the same or approximately the same point in time. • E.g., Building permits in January • Time series data are collected over several time periods. • E.g., Building permits each month

  13. Data Sources • Existing Sources – data already exists. • Statistical Studies – data obtained through a study. • Experimental Studies – variable of interest identified and other variables controlled. • Observational studies – no attempt is made to control or influence the variables of interest.

  14. Descriptive Statistics • Data summarized and presented in a form that is easy for the reader to understand. • Tabular, graphical, or numerical. Average Tune-up = $79

  15. Statistical Inference • Use data from a sample to make estimates or test hypotheses about a population.

  16. Statistical Inference • Population – set of all elements in a particular study. • Census – collects data about entire population. • Sample – a subset of the population. • Sample survey – collects data for a sample.

  17. Statistical Inference Population Sample Statistics about sample Statistics about the sample provide an estimate of the population.

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