UW-Madison PSYCH 210 - Central Tendency (5 pages)
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Central Tendency
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- Lecture number:
- 4
- Pages:
- 5
- Type:
- Lecture Note
- School:
- University of Wisconsin, Madison
- Course:
- Psych 210 - Basic Statistics for Psychology
- Edition:
- 1
Unformatted text preview:
PSYCH 210 Lecture 4 Outline of Last Lecture I Finish Summation Notation II Frequency Distributions III Graphing IV Percentiles and Percentile Ranks Outline of Current Lecture II Percentiles and Percentile Ranks a Interpolation III Central Tendency a Mode b Mean c Median Current Lecture I Percentiles and Percentile Ranks a Descriptive Statistics b Used for relative standing in a population c Percentile i Raw Score x ii Score associated with a given cumulative percentage C d Percentile rank i A cumulative percentage C ii The percentage of scores falling at or below a given raw x score e Ex What is the raw score x associated with the 95th percentile rank i Table 1 Raw scores are NOT class intervals 2 If data is continuous C will be associated with upper real limit of interval a Class Interval from table correlating with 0 95 C 60 69 b Raw score 69 5 f Ex What is raw score x associated with the 50th percentile rank These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute i 50th percentile not listed in table ii Interpolation Educated guess using method to obtain best estimate 1 Set up what we know from the table x C 49 5 URL 60 50 39 5 URL 30 2 49 5 39 5 10 a Unit span between top and bottom X 3 60 30 30 unit span a Unit span between top and bottom C 4 60 50 10 a Unit span between top and middle desired C i Can also do bottom to middle C span 5 10 30 x 10 1 3 x 10 x 3 333 6 49 5 3 333 46 17 Raw score 46 17 g What is the percentile rank for a raw score of x 45 i Interpolation 1 Two ways to think about it LRL URL ORa URL of CI URL of next lower class interval 2 3 4 5 II x C 49 5 60 45 39 5 30 60 30 30 unit span 49 5 39 5 10 unit span 49 5 45 4 5 units 4 5 10 x 30 45 30 x 13 5 6 60 13 5 C 46 5 or 0 465 Central Tendency a Summary Statistics for most typical score in distribution defined in 3 different fashions i Mode 1 The most common score in a distribution highest frequency 2
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