data and statistics
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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. - PowerPoint PPT PresentationTRANSCRIPT
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Data and Statistics
Chapter 1BA 201 – Fall 2010
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Statistics
Numerical facts such as averages, medians, percents, and index numbers.
Art and science of collecting, analyzing, presenting, and interpreting data.
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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.
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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.
Elements, Variables, and Observations
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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
Stock Annual Earn/Exchange Sales($M) Share($)
Data Sets, Elements, Variables, and Observations
Dataram EnergySouth Keystone LandCare Psychemedics
N 74.00 1.67
Variables
Elements
Data Set
Observation
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Scales of Measurement
Nominal
Ordinal
Interval
Ratio
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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
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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
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What You Can Do With Scales
Compute Nominal Ordinal Interval Ratio
Frequency distribution. Yes Yes Yes YesMedian and percentiles. No Yes Yes YesAdd or subtract. No No Yes YesMean, standard deviation, standard error of the mean.
No No Yes Yes
Ratio or coefficient of variation. No No No Yeshttp://www.graphpad.com/faq/viewfaq.cfm?faq=1089
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Categorical or Quantitative DataCategorical (or Qualitative) Grouped by categories Numeric or non-
numeric Nominal or ordinal
Quantitative How much or how
many Numeric Interval or ratio More statistical tests
available
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Scales of Measurement
Categorical Quantitative
Numeric NumericNon-numeric
Data
Nominal
Ordinal
Nominal Ordinal Interval Ratio
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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
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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.
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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
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Statistical Inference
Use data from a sample to make estimates or test hypotheses about a population.
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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.
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Statistical Inference
Population Sample
Statistics about sample
Statistics about the sample provide an estimate of the population.
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