What do representative values tell us?
They summarize a dataset with a single value that reflects the center or typical score.
Are some measures of representative values better than others? When? Why?
Yes. Mean uses all data and is best for symmetric distributions; Median is better for skewed data or outliers; Mode is useful for categorical data.
How do you calculate the median when you have an odd number of values in a set of data?
Order values from smallest to largest and select the middle value.
What does variability tell us?
How spread out the data are and how much scores differ from each other.
What are the steps for calculating variance?
1) Find the mean; 2) Subtract mean from each score; 3) Square deviations; 4) Sum squares; 5) Divide by N (population) or n−1 (sample).
Why is the standard deviation the most widely use method for describing variability?
It uses all scores, is in original units, and reflects average distance from the mean.
What are the steps for computing the standard deviation?
1) Compute variance; 2) Take the square root of the variance.
How do you convert a raw score to a Z score?
Subtract the mean from the raw score and divide by the standard deviation: z = (X − μ) / σ.
How do you convert a Z score to a raw score?
Multiply the Z score by the standard deviation and add the mean: X = μ + zσ.
