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As revised and posted after class.
WEEK 8 – Wed, Oct 20
DESCRIPTIVE STATISTICS and GRAPHICAL DISPLAYS
(Background material is in Chapter 1)
Overview of Data Types and Data Collection
(Chap 1, Sec 1)
Measurement processes applied to subjects or entities produce data.
Usually many
variables are measured for which data are recorded.
You must understand the measurement process and the selection process (and the
possible filtering of subjects out of the study after their selection) before you can truly
evaluate the importance and usefulness of the data.
Discuss and give examples of each of the following types of data.
Categorical Data (sometimes coded numerically)
Numerical Data
Measurement
Process
Selection
Subjects
Data
1
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View Full DocumentNumerical Data Distributions – Percentiles and Quartiles
(Chap 1, Sec 2)
Review of Percentiles for Probability Distributions.
We learned how to get
percentiles of normal distributions in Chapter 4.
Recall that there we were working with
random variables that take values on the line (numerical values) and the concept of a
100pth percentile, say, p = .95 for the 95
th
percentile.
This percentile is a position x that
splits the distribution into two parts with P(X ≤ x) = .95 and P(X > x) = .05.
Technically, this is a solution x to the equation F(x) = .95 where F is the cumulative
distribution function of the continuous random variable.
Example. N(90, 17).
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 Spring '08
 Anderson

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