[PSY 207] Comprehensive Final Exam guide including any lecture notes, textbook notes and exam guides.find more resources at oneclass.com
What is a frequency distribution?
What do we do with pages of numbers?
Organize scores into a comprehensible form
A frequency distribution is an organized tabulation of the number of individual scores observed
at each value or category on the scale of measurement.
Why are frequency distributions useful?
They show whether the scores are generally high or low, and where the major concentration of
scores is located.
We can also present:
Proportion = p = f/N
Percentage = p(100) = f/N(100)
Grouped Frequency Distributions
When a set of data covers a wide range of values:
– it is unreasonable to list all of the individual scores
– To simplify the frequency distribution we group the scores into intervals.
To produce a grouped frequency distribution you have to make two decisions:
The number of intervals
2 square root (N) if N 10
10Log(N) if N 100
N=250 10Log(250) = 10 x 2.40 = 24
N=125 10Log(125) = 10 x 2.10 = 21
The size of the intervals
range of scores/# intervals
then round to a convenient number
100-60/24 = 1.67
here round up to 2
For a histogram, a vertical bar is drawn above each score so that
The height corresponds to the frequency
The width extends to the real limits of the score
What is a real limit?
Real Limits: boundaries of the intervals for scores that are represented on a continuum.
The real limit separating two adjacent scores is exactly halfway between the scores.
Each score has two real limits
the upper and lower real limit
A single dot is drawn above each score so that
The dot is centered above the score
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