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Parameter
quantity calculated from a population
Statistic
quantity calculated from a sample
Sigma: Population Standard Deviation
Sigma
Symbol for population deviation
^{2}
Sigma Squared: Population Variance
Sigma Squared
Population Variance
mu: population mean
mu
population mean
Population Variance
variance of the population - usually estimated, rarely computed
Population
Set of all objects that we're interested in researching
Standard Deviation
square root of the variance
Sample
Subset of the population; set of the actual observations
Significance
results are unlikely to have occured by chance alone
Random Sample
each member of the population has an equal chance of being included
sample mean
s^{2}
Sample Variance
s
Sample Standard Deviation
X
Individual Observation; Raw Score
Central Limit Theorem (CLT)
Given a population with finite mean mu and finite variance sigma squared, the sampling distribution of the mean approaches a normal distribution with the mean mu and variance sigma squared divided by N, as N, the sample size, increases
Measures of Central Tendency (3 Ms)
Mean
Median
Mode
Mean
arithmatic average: The sum of the scores divided by the number of scores
Median
Middlemost score
Mode
the most frequently occuring score
abscissa
x axis; horizontal axis
ordinate
y axis; vertical axis
Histogram
bar chart
N
the number of observations
Normal Distribution
Bell Curve; Mesokurtic
Frequency Distribution
Frequency Polygon
Skewed Distribution - Skewness
a skewed bell curve; a measure of the degree to which a distribution is asymmetrical
Kurtosis
levelness/flatness around the mode of a frequency distribution
Leptokurtosis
more scores in the tails and fewer in the middle as compared to the corresponding normal distribution
most commom with small sample sizes
Platykurtic Distribution
more scores in the middle and fewer scores in the tails as compared to the normal corresponding distribution