Exam I Flashcards
data
points classified by variables
variable
characteristic of object
- qualitative
- quantitative
qualitative
categorical
sex, treatment groups, ethnicity
quantitative
numerical
weight, height, bp
categorical
nominal
ordinal
quantitative
interval
ratio
nominal
no order
y/n, m/f, white/black/hispanic
ordinal
ranked to give order
mild/moderate/severe, poor/fair/good/excellent
interval
level clearly defined by distance bw variables
pH, C
ratio
values equally spaced w an absolute zero point
weight, K
discrete vs. continuous
whole #s vs decimals
people vs time
statistic
measure of sample
calculated
parameter
measure of population
inferred
descriptive statistics
summarize sample of population
inferential statistics
use sample statistics to infer about population
of intervals
k=1+3.322log(n)
round up
interval width
w=range/k
histogram distribution
symmetric
left tail/negative skew
right tail/positive skew
bimodal
measures of central tendency
mean
median
mode
measures of dispersion (variability/spread)
range variance standard deviation coefficient of variation mean absolute deviation
variance
s^2=Z(x-mean)/n-1
coefficient of variation
CV=s/mean*100%
mean absolute deviation
MAD=Zabs(x-mean)/n
percentile
pth percentile=p(n+1)/100
interquartile range
IQR=Q3-Q1
symmetric box & whisker
mean=median
skewed box & whisker
left: mean < median
right: mean > median
outlier
> Q3+1.5IQR
<Q1+1.5IQR
outside 3s from mean
numerical summary
min, Q1, Q2, Q3, max
symmetric/no outliers: n, mean+-std
skewed/outliers: n, mean+-IQR
