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PSYC 210 Study Guide - Midterm Guide: Squared Deviations From The Mean

Department
Psychology
Course Code
PSYC 210
Professor
Cathy Mc Farland
Study Guide
Midterm

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In-class notes
Lecture 2: January 16, 2012
Summation Notation
- = X1 + X2 + X3 + … + XN
i = 1 lower limit of the summation
Algebraic Rules of Summation
- Summary of the constant
oThe sum of k occurrences of constant c
oK = # of constants; k times the constant
o = c + c + c + … + c
= kc
oThis is just simple multiplication but they're trying to make it look complicated
- Summing cX
oThe sum of the k products, where each product is obtained by multiplying a constant by the score
on the variable =equals= the constant times the sum of the variable
o = cX1 + cX2 + … + cXk
= c (X1 + X2 + … + Xk)
= c
- Distributive laws over addition & subtraction
- the summation operator can be distributed across variables or constants when they are added or
subtracted from one another
BUT
Sum of products not generally equal to product of sums
≠ ( )( )
Displaying Data
- Raw Data or Data Scores – the scores obtained from sampling units before the scores are analyzed
statistically
-Frequency Distribution – a set of possible values of a variable in a dataset, along with the count of how
often each value occurs
- Frequency of occurrence – the number of cases in a sample with scores at a specified value
- Relative frequency (fR) – the proportion of the sample with scores at a specified value, then multiplied by a
hundred
ofR =
N is the total # of people in the sample
- Cumulative Frequency – the number of cases with scores at or below the specified value
ofcr =
- Cumulative Relative Frequency – the proportion of the sample with scores at or below the specified value
ofcr =
SCALES Classify Order Equal
distances
True
zero
Nominal X
Ordinal X X
Interval X X X
Ratio X X X X
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