Chapter 3 - Properties of Distribution Flashcards
what does frequency distributions tell us?
tells us about the relative standing of individual scores/intervals on some variable of interest
why are measures of variability required to evaluate the differences between the averages?
to see the exact scores, have more information, make better conclusions, etc.
define central tendency
that is typical of the scores in a distribution
define mean
arithmetic average (sensitive outliers)
define median
exact middle value (not effected by outliers)
define mode
most frequent value (can be multiple)
define normal distribution
unimodal, symmetrical distribution (bell-curve)
define skewed distribution
asymmetrical, mean, median, and mode not aligned
what is the difference between left skew (negative) and right skew (positive)?
left skew = long tail is to the left
right skew = long tail is to the right
define kurtosis.
sharpness of the peak of a distribution.
define the tree different types of kurtosis.
- Normal distribution
is Mesokurtic - Sharp peaked are
Leptokurtic - Flat peaked are
Platykurtic
define mean (sample).
- The mean is a balance point:
- If we subtract the mean from each
score in the set, their sum would equal 0
X - 64 = { -23, 0, -9, 15, 17 }
(-23) + 0 + (-9) + 15 + 17 = 0 - Whenever we subtract the mean from
all numbers in the set, some differences
will be positive and other negative - But the sum of the difference scores will
be equal to 0
what is the difference between the mean of a population and of a sample?
population = parameter
sample = statistic
what are the different symbols?
- Greek = Population Parameters
- Roman = Sample Statistics
- m is an estimate of µ
what are the advantages and disadvantages?
- Advantages:
- Function of every score
- Always has a unique value
- Most stable measure of central tendency
- Disadvantages:
- Influenced by extreme scores (AKA Outliers)
- Only appropriate for interval or ratio scales
- Function of every score
