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Wittenberg University - 2010 Psych107Q - Statistics Test 1
Material for Dr. Cliff Brown's Test 1
33
Mathematics
Undergraduate 2
01/27/2010

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Term
population
Definition
the total collection of objects, events, or organisms that have (or could have) a score value for some attribute
Term
sample
Definition
a subset of a population (e.g. random, stratified)
Term
variable
Definition
Uppercase letters (e.g., X, Y, Z); subscripts to identify specific observations (e.g., X3 for the third observation on X)
Term
independent variable
Definition
manipulated by the experimenter
Term
dependent variable
Definition
behavior of participant measured by the experimenter
Term
data
Definition
the measurements that are made on the subjects of an experiment
Term
statistic
Definition
a number calculated on sample data that quantifies a characteristic of the sample
Term
parameter
Definition
a number calculated on population data that quantifies a characteristic of the population
Term
descriptive statistics
Definition
methods to organize and summarize data (e.g. monthly sales, batting average, correlation between SAT and GPA)
Term
inferential statistics
Definition
drawing inferences about a population on the basis of a sample
Term
scales of measurement
Definition
nominal scale (no properties; ex. Sex: 1 = male, 2 = female...); ordinal scale (magnitude; ex. Class rank: 1st, 2nd, 3rd…); interval scale (magnitude, equal intervals; ex. Degrees F and degrees C); ratio scale (magnitude, equal intervals, and absolute zero; ex. Time, weight, length)
Term
apparent limit
Definition
the lowest and highest score values in a class interval
Term
real limit
Definition
one half of a measurement unit above and below the apparent limits
Term
midpoint
Definition
halfway point between the lower and upper apparent limits
Term
interval width
Definition
lower apparent limits are evenly divisible by this number
Term
I values
Definition
must not be too many or they will be too complex, or too few because it will be too simple
Term
percentile
Definition
the score (X) at or below which a certain percentage of the cases fall
Term
percentile rank
Definition
a value indicating the percentage of cases falling at or below a given score
Term
mean
Definition
Raw data: add the scores and divide by N
Grouped data: multiply each midpoint by f, add up each f X and divide by N

Properties:
Σ (X – ) = 0
Σ (X – )2 is at a minimum
Sensitive to all scores in the distribution
Stable with regard to sampling fluctuations
Term
median
Definition
Raw data: put them in order and find the one in the middle (odd N) or the average of two in the middle (even N)
Grouped data: calculate X50
Term
mode
Definition
Raw data: easy, just count them, more than one mode is possible
Grouped data: the midpoint(s) of the interval(s) with the largest frequency (f)
Term
skew
Definition
the degree to which a distribution departs from symmetry about its mean value
Term
μ
Definition
mean for a population parameter
Term
σ
Definition
standard deviation of a population parameter
Term
σ²
Definition
variance for a population parameter
Term
(capital)S
Definition
standard deviation for a sample statistic
Term
(capital)S²
Definition
variance for a sample statistic
Term
xbar
Definition
mean for a sample statistic or unbiased estimator
Term
(lowercase)s
Definition
standard deviation for an unbiased estimator
Term
(lowercase)s²
Definition
variance for an unbiased estimator
Term
unbiased estimator
Definition
a sample statistic that in the long run neither overestimates not underestimates its corresponding population parameter
Term
variability
Definition
dispersion, scatter
Term
Σ(x-xbar)
Definition
sum of deviations from the mean (always equals 0)
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