STA261 Final Exam Cheat Sheet
Kimberly Glennon
Binomial Distributions/Random Variables
: must have 4 things—fixed # of trials (n), each trial must be independent, each trial
has 2 outcomes (success or failure), must have a constant probability of success. Can use if np>10 and n(1p)>10
# of possible outcomes that have exactly x successes out of n: 3! / x!(3x)! times (1/4)
x
(3/4)
3x
when n=3 and p=1/4
M
x
= np
and
SD
x
= SqRoot of np(1p)
Normal Distributions/Random Variables
: standardizing (1,2,3 SDs/68, 95, 99.7 rule) and zscore = (valuemean)/SD
Parameter vs Statistic: P is a number that describes the population; S is a number that is computed from a sample.
Sampling Distributions
: focus on difference between values of a variable for a sample and its values for the entire population.
if change sample size n, will change variability. Larger sample sizes have less variability.
SD of all sample proportions is the square root of (p(1p) / n); Sample Mean (xbar) is same as population mean.
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 Fall '08
 BEAL
 Binomial, Probability

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