Vocabulary
Measures how spread-out or clustered scores are
Variability
Variability squared
Variance
n-1
degrees of freedom
Distance between largest and smallest score
Range
Shows how much individual data points differ from the mean.
Standard Deviation
What are some factors that can affect variability (at least 1)?
Extreme scores, open-ended distributions, sample size
∑(xᵢ - x̄ )²
Sum of Squares
What information can a z score give?
Determines how well a sample represents a population
True/False
Z-scores that are above the mean are always positive
True
Number of possible scores free to vary AKA (n-1)
Degrees of freedom
What is a disadvantage of the range?
Sensitivity to outliers
σ2 = SS/N
Population variance
Every raw score has a corresponding z-score
True
True or False
Population data uses degrees of freedom in an attempt to remove bias.
False, sample
1 disadvantage OR advantage of each (mean, mode, and median)
Mean- sensitive to outliers; Mode- ignores non-common values; Median- doesn't use all data points
(x- μ) / σ
Z score formula
How do you find standard deviation?
Square root of the variance (or give the formula)
Each individual in the population has an equal chance of being selected.
Random Sampling
This happens to variability when a sample size gets smaller
Increases variability
√ ( Σ(xi - μ)² / N )
Population Standard Deviation
In a distribution of z-scores the mean is always ___ and the standard deviation is always ___.
0 and 1
Sampling technique, Sample size, & Variability within the population