PSYC 2300 Lecture Notes - Lecture 10: Central Tendency, Frequency Distribution

15 views3 pages
30 Aug 2018
School
Department
Course
Professor
Central Tendency
1. Overview of central tendency
a. Central tendency: statistical measure to define center of a distribution
b. Purpose: find single-most typical or representative score of entire group
c. Mean3 definitions
i. Sum of scores divided by # of scores in data
ii. Average amount
iii. Balancing point of distribution
2. Mean
a. Computed in the same manner because it’s the sum of all scores divided by the #
of scores in the data
b. Population:
c. Sample:
d. Weighted mean
i. 2 or more groups with unequal sample sizes
ii. 3 ways to computeuse of method depends on available data
1. If you have all raw data, obtain average student grade by
averaging all grades without regard to classes
2. If only group means and # of individuals in each group are
available, weight class means by # students in a class


3. If you have 2 sets of sums and sample sizes, combine information

iii. Which one do you use?
1. Raw data givenmethod 1
2. Group sample sizes and means givenmethod 2
3. Sum of x’s and sample sizes givenmethod 3
e. Characteristics of mean
i. Changing value of a score changes the mean
ii. Introducing a new score (or removing a score) usually changes the mean
unless score added or removed is exactly equal to the mean
iii. Adding or subtracting a constant from each score changes the mean by
the same constant
iv. Multiplying or dividing each score by a constant multiplies or divides the
mean by that constant
3. Median
a. Median: midpoint of scores in a distribution
b. Listed in order from smallest to largest divides scores into 2 groups of equal sizes
c. Also called 50th percentile
d. Because it ignores most of the data, uninfluenced by extreme scores
e. Cannot be manipulated algebraically
f. Locating medianodd # of scores
Unlock document

This preview shows page 1 of the document.
Unlock all 3 pages and 3 million more documents.

Already have an account? Log in

Get OneClass Notes+

Unlimited access to class notes and textbook notes.

YearlyBest Value
75% OFF
$8 USD/m
Monthly
$30 USD/m
You will be charged $96 USD upfront and auto renewed at the end of each cycle. You may cancel anytime under Payment Settings. For more information, see our Terms and Privacy.
Payments are encrypted using 256-bit SSL. Powered by Stripe.