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Class notes Chapter 3 STATS-2126 Essentials of Statistics for the Behavioral Sciences, ISBN: 9780357035580
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- Statistics (STATS2106)
- Institution
- Laurentian University (LU )
lecture/chapter note (fall 2020)
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1 of 10 October 10, 2020Statistics Chapter 3 Notes
3-1 Overview
Central Tendency: A statistical measure to determine a single score that defines the centre of a
distribution.
Statistical measure to determine a single score tat defines the midpoint of a distribution
(mindtap def)
The goal of central tendency is to find the single score that is more typical or most
representative of the entire group.
3-2 The Mean
Mean: The sum of the scores divided by the number of scores. It is the arithmetic average.
Sample Mean Formula Population Mean Formula
M => sample ∑X ∑X
M= μ=
n Sample N Population
Example 3.1 pg 77 ∑X
μ=
N=4 scores, 3,7,4,6 N
20 Therefore, the
N=3+7+4+6 = mean is 5 of this
= 20 4 population
=5
Alternative Definitions for the Mean
1. Dividing the total equally
Think of the mean as an amount each individual receives when the total (∑X) is divided equally
among all the individuals (N or n) in the distribution
Example 3.2 pg 77
A group of n=6 children buy a box of game cards and it contains 180 cards.
If the children divided the cards equally between themselves, how many will each child get?
total # of cards
∑X 180 Therefore, each kid
= = = 30 will get 30 cards
# of children n 6
If they decided to sell their cards for an average of M=5$ per child, what is the total amount of
money for the whole group?
n=6 6 kids make 5$ ∑ X 30 Therefore, they would
M= = = 5$ make $30 all together
M=5 6(5$)=30$ n 6
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