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Gravity
Exam 2 notes
Terms in this set (22)
Probability
Can be viewed in several different ways - no general agreement on a specific meaning
Analytic view of Probability
If an event can occur in A ways and fail to occur in B ways - and all possible events are equally likely - the P of event occurring = A / (A+B), and the P of the event NOT occurring = B / (A+B)
Frequentist view of probability
Or P(event) = limit of the relative frequency of the event as the number of draws approaches infinity
Subjective probability
Person's subjective belief in the future occurrence of an event (no math basis, but based on judgment; very often used in human decision-making; based on interpretation of past experiences)
Sample with replacement
item is drawn from set; items is replaced in set prior to drawing another item
Event
Outcome of trial or draw (drawing chip from hat; rolling dice; selecting lottery numbers; flipping a coin)
Dependent events
the occurrence of one event influences the P(occurrence of other event)
Independent events
the occurrence of one event has no effect of the P(occurrence of other event
Mutually exclusive events
the occurrence of one event precludes the occurrence of the other event
Exhaustive events
all the events occurring represent all possible outcomes of event (ex. Dice: 1,2,3,4,5,6)
Additive law of probability
given set of mutually exclusive events, P(event A or B) = P (A)+P(B)
Multiplicative law of probability
given set of mutually exclusive events, P(A and B) = P(A) X P(B)
Joint probability
The probability of the co-occurrence of 2 or more events If 2 events are independent, probability of their joint occurrence is found with multiplicative law of P; If 2 events are not independent, probability of their joint occurrence is complex to compute
Conditional probability
The probability that one event will occur, given the occurrence of some other event.
Unconditional probability
P of an event, ignoring the occurrence or nonoccurrence of any other event
Risk
Probability that something will happen (probability of being robbed = risk of being robbed)
Risk ration
the ration of two risks (i.e., ration of risks of 2 different groups for the same event)
Odds
number of occurrences of event divided by number of non-occurrence
Odds ratio
the ratio of two odds (odds of women having heart attack / odds of men having heart attack)
Discrete variable
in theory: countable number of values; in practice: small number of values
Continuous variable
in theory: unlimited number of values; in practice: large number of values
Density
height or curve for given value of X; related to P of observation falling some small interval around X; relative frequency in interval; not same as P. Must compute area under curve for some small interval around the X of interest; precisely X has no density! In calculus, integrate the function for this curve for that interval (i.e., from X=24.5 to X=25.5)
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