Chapter 4: Measures of Central Tendency Flashcards
Sample Mean?
X bar = x1+x2+x3…..XN/N
Mean?
arithmetic average
x-bar
sum of the set of scores divided by the number of scores summed…
X= ΣΧ/Ν
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<Mode
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
