PSYC 331 Lecture 10 -- Central Tendency

# PSYC 331 Lecture 10 -- Central Tendency - PSYC 331 Lecture...

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1 PSYC 331 Lecture 10 Central Tendency

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2 Overview In this lecture we will discuss: The Mean The Median The Mode Selecting a Measure of Central Tendency Central Tendency and the Shape of the Distribution Weighted Means
3 Central Tendency Goal – describe the 'average' of a variable ( X ) for a group of units/subjects (e.g., a sample) with a single measure, or value. Mean, Median, and Mode — Three measures of central tendency. Mean: What people typically think of when they talk about the ‘average’ Median: the 50th percentile – the point below which exactly 1/2 of the scores lie. Mode: the score or category with the greatest frequency.

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4 The Mean Computed by: Summing all the scores of interest Dividing by the total number of scores Note differences when computing population mean vs. sample mean: Population μ = N X N 1 i i = Sample : or M = X n X n 1 i i =
5 Characteristics of the Mean 1. Changing a single score , or adding a new score , will change the value of the mean. 2. Adding, or subtracting, a constant to each score in the distribution will have the result of adding or subtracting that same constant to the mean. 3. Multiplying or dividing each score by a constant results in the mean being multiplied or divided by the same constant. 4.

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## This note was uploaded on 01/15/2010 for the course PSYC 331 taught by Professor Dianealonso during the Fall '09 term at UMBC.

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PSYC 331 Lecture 10 -- Central Tendency - PSYC 331 Lecture...

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