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## PowerPoint Slideshow about ' Data and Statistics' - sahkyo

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Presentation Transcript

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 – 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

http://www.graphpad.com/faq/viewfaq.cfm?faq=1089

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

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

Statistics about sample

Statistics about the sample provide an estimate of the population.

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