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Dawn Chen
October 2, 2009
Information about the Section and Course
The purpose of the discussion section is to clarify lecture material, answer student
questions, and show how to solve problems.
Podcasts for the course can be found at
http://www.bruincast.ucla.edu
, scroll down to
find “Psychology 100A – Lec 2.”
Ways of Categorizing Data
It is important to know how to categorize data so that we can choose the appropriate
statistical analysis and interpretation for the data.
Three ways of categorizing data were
introduced in lecture:
(1)
Qualitative vs. quantitative
(2)
Nominal vs. ordinal vs. interval vs. ratio
(3)
Discrete vs. continuous
Qualitative data are about qualities that the subject under study possesses (e.g., a person’s
gender, ethnicity, or favorite flavor of ice cream).
Qualitative data are measured using nominal
scales, in which there are different named categories that each piece of data could fall into.
Because of this, qualitative data are also discrete.
Quantitative data are numerical data or quantities about the subject under study.
Quantitative data are measured using three different scales: ordinal, interval, and ratio.
Ordinal
data are always discrete, whereas interval and ratio data could be discrete or continuous.
This is
summarized in the following diagram:
Distinguishing between ordinal, interval, and ratio scales
Let’s say that a psychologist develops a scale to measure a person’s level of depression.
This is an example of an interval scale.
That is, the difference in depression level between
someone who scores a 5 on the scale and someone else who scores a 10 on the scale is the same
as the difference in depression level between the person with a score of 10 and someone else
with a score of 15.
This is because each unit on an interval scale has the same length, whereas
on an ordinal scale, the difference between someone with a rank of 1 (least depressed) and
Qualitative
Quantitative
Nominal
Discrete
Ordinal
Discrete
Interval
Ratio
Dis.
Dis.
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This note was uploaded on 09/24/2010 for the course STATS 13a taught by Professor Chen during the Spring '10 term at UCLA.
 Spring '10
 Chen
 Statistics

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