Chapter 4: Measures of Central Tendency Flashcards
Sample Mean?
X bar = x1+x2+x3…..XN/N
Population mean?
mew= X1+x2+x3….XN/n
Mean Properties?
sensitive to values of all scores in distribution..
sum of the deviations about the mean = zero
if you subtract the mean from each score and than sum the values…it will equal zero…
Outliers?
extreme points that shift the mean…..
Σ(Χ-χ)2 = sum of squared deviation..
basically it will be smaller than other value substituted in instead of the mean
the further x bar gets from the actual mean the higher the deviation is
Mean is the least or most subjective to variability.
Mean is least!
Mean
Overal Mean?
mean for many samples…
(mean of group 1)(number of scores) +………
divided by total number of scores from all groups
Median
point with which fifty percent of scores fall in.
Mdn = mean
less sensitive to extreme scores..
to calc for it just do P50
Mode?
most frequent score in distribution
no math
unimodal means only one
bimodal : two that are equally frequent
Symmertry?
bell shaped curve: middle = median, mode, mean!
in positive skew …mean is shifted near the right
negative skew…mean shifts left….
Mean : scale ?
Mode : scale?
Median: scale?
mean: ratio or interval
mode: nominal
median: ordinal
Mean of frequency distribution formula?
Σf(MP)\N
Mp= midpoint of URL and LRL
F = frequency
Sum all midpoints mult by their f and divide by total number of scores
Range?
Highest URL- lowest LRL
Deviation scores
How far each raw score is from mean
Variance
Σ(x-Χ)/Ν
