Data and Statistics

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# Data and Statistics - PowerPoint PPT Presentation

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

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
• 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.
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.

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

Scales of Measurement

Nominal

Ordinal

Interval

Ratio

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
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
What You Can Do With Scales

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

Scales of Measurement

Data

Categorical

Quantitative

Numeric

Numeric

Non-numeric

Nominal

Ordinal

Nominal

Ordinal

Interval

Ratio

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
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.
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

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

Population

Sample