descriptive statistics Flashcards
what are central tendency
mean, median, mode
how is spread measured
quantiles, quartiles and percentiles, variance and standard deviation
how is variance calculated
his is called the 2nd moment = ∑ [distance from mean]2 to each data point /
number of data points = variance
how is standard deviation calculated
square root of variance
what is a z-score and what does it do
enables fair comparison of deviations
creates a ratio with respect to standard deviation
deviation from mean
what measures of shape are there
skewness and kurtosis
what is skewness
where most the data points are
can either be postive or negative
postive skew = peak on left
negative skew = peak on right
what is kurtosis
kurtosis is how sharp a distribution is
always postive
how is an outlier identified
z-score and IQR
z-score = outlier if 3 more or 3 less
IGR if greater the 1.5 of 3rd quartile
or smaller than 1.5 IQR of 2nd quartile
what is cumulative probability
probability that a value falls within a range
what is an example of cumulative probability
Pr ( 0 ≤ k ≤ 3 | 10, 0.5) = Pr (0 | 10, 0.5) + Pr (1 | 10, 0.5) + Pr (2 | 10, 0.5) + Pr (3 | 10, 0.5)
= 0.172
how is two-tailed cumulative probability calculated
by deviation of k from mean (k) > 10
what is continuous distribution also known as
normal or gaussian
