STAT 371: Stats 371 I
46 Cards in this Set
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Sample
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a representation to the target population.
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Populations
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the entire collection of individuals or units that a researcher is interested in
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parameter
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a quantity describing a population. constant and unknown
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random sample
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should be accurate and precise
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accurate
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unbiased
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precise
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precise
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convience bias
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collects items only be convience
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volunteer bias
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behavior/opinions affects whether they are sampled
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Categorical
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qualitative variable
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nomial
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variety
-no order
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ordinal
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categories have an inherent order
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Numerical
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quantitative value
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discrete
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whole numbers
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continuous
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can be any measurement
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response
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are considered outcomes
-dependent
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explanatory
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thought to potentially affect outcomes
-independent
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IQR
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the inter quartile range= a range between the 1st and 3rd quartiles
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mean
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is more sensitive to extreme values
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median
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more resistant to extremes. Used as middle value of boxplot
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standard deviation
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the square root of sample variance
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sample variance
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the sum of squared deviations
-variation from mean
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Elementary outcome
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the complete description of a single result from the exeriment
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sample space
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the entire group of elementary outcomes
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intersection
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"A&B" consists of outcomes in both A and B
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Union
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"AorB" consists of outcomes in either A, or B, or both
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Complement
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"NotA" consists of outcomes that are not in A
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Mutually exclusive
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events that have no common elementary outcomes (can't happen simultaneously)
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A or B
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P(A)+ P(B)
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Conditional probability
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the probability of event A given B, is the probability of A given that B occured
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A/B
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P(A&B)/P(B)
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A and B
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P(A/B) X P (B)
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independent events
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if occurrence of one event does not affect the chance that the other will happen
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B/A
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(P(A/B) X P(B))/(P(A/B)XP(B)+P(A/notB)XP(notB)
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random variable
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is a variable that depends on outcomes of a chance situation.
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probability distribution
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one Random Variable should assign probability to all values of the Random Variable
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My
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E(y)=Sumy=(P(Y=y))
p(y=0)+p(y=1)
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Variance (θ²y)
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E(Y-M)²=Sum((Y-M)²)*P(Y=y))
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Standard Deviation (θ)
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√Sum((Y-M)²)*P(Y=y))
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My
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αMx+B
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standard deviation
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/a/θx
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Binomial distribution
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weighted distributions of probability
y-Bin(n,p)
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Bin
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probability of getting J successes
-(nj)p^j(1-p)^(n-j)
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Assumptions
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-trials have exactly 2 outcomes
-probability of success (p) is same for all trials
-# trials, n, is fixed in advance
-all trials are INDEPENDENT
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normal distribution
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-many random varaible have bell shaped distribution
-normal density curve is a good approximation
-analytical form of bell curve
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N (normal)
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y-n(My,θy)
-symmetric around its mean
-single node
-probabilty density highest at mean
-probability measured by area under curve
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Z
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indexes a number of standard deviations from the mean
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STAT 371: Stats 371 I