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Stat 212
Exam 1 (Chapter 5)
22
Mathematics
Undergraduate 2
09/29/2009

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Term
Random phenomena
Definition
  • outcome is uncertain
  • short-run proportion of occurences very random
  • Long run more predictable
  • Probability quantifies long-run randomness
Term
Law of large numbers
Definition
  • as number of trials increase, proportion of occurrences of any given outcome approaches a particular number
Term
Independent Trials
Definition
  • outcome of any one trial is not affected by the outcome of nay other trial
Term
Finding Probabilities
Definition
  • Calculate theoretical probabilities based on assupmtions about the random pehnomena
  • Observe many trials of random phenomenon and use sample proportion of the number of occurences as probability
Term
Relative frequency
Definition
  • Long run proportion of times that the outcome occurs in a very large number of trials
Term
Subjective probability
Definition
  • When long-run trials not feasible
  • probability of outcome is your degree of belief the outcome will occur
    • Bayesian statistics uses subjective probability.
Term
Sample Space
Definition
  • For random phenomenon:
    • sample space is the set of all possible outcomes
Term
Event
Definition
  • subset of sample space
  • even corresponds to particular outcome or a group of possible outcomes
Term
Probabilities for a sample space
Definition
  • Each outcome in sample space has a probability
    • The probability of each individual outcome is between 0 and 1
    • total of all individual probabilities equals 1
Term
Probability of a Event
Definition
  • Probability of an event A = P(A)
  • P(A) = (number of outcomes in event A)/(Number of outcomes in the sample space)
Term
Complement of events
Definition
  • Complement of event A consists of all outcomes in sample space that are not in A
  • Probabilities of A and of Ac (complement) sum to 1
  • P(Ac) = 1- P(A)
Term
Disjointed EVents
Definition
  • events do not have any common outcomes
Term
Intersection of events
Definition
  • Outcomes that are common in both events
Term
Union of events
Definition
  • Consists of outcomes that are in even A or B or in both A and B
Term
Probability of Union of 2 events
Definition
  • Addition Rule
    • For the union of 2 events
      • P(A or B) = P(a) + P(B) - P(A and B)
    • If the events are disjoint, P(A and B) = 0
      • Thus: P(A or B) = P(A) + P(B)
Term
Probability of Intersection of Two Events
Definition
  • Multiplication Rule
    • For the intersection of 2 independent Events A and B
      • P(A and B) = P(A) X P(B)
Term
Conditional Probability
Definition
  • For events A and B, Conditional probability of event A give that event B has occurred is
  • P(A|B) = P(A and B)/P(B)
Term
Pultiplication Rule for Finding P(A and B)
Definition
  • P(A and B) = P(A|B) x P(B)
  • P(A and B) = P(B|A) x P(A)
Term
Efinition of Independent Events using conditional probability
Definition
  • 2 events A and B are independent if probability that one occurs is not affected by the other
  • Independent if
    • P(A|B) = P(A) or P(B|A)=P(A)
    • P(A and B) = P(A) x P(B)
Term
Is a "Coincidence truly an unusual event?
Definition
  • Law of very large numbers states that if something has a very large number of opportunities to happen, occasionally it will happen even if unusual
Term
Probability Model
Definition
  • specifies possible outcomes for sample space and provides assumptions on which probability calculations for events composed of these outcomes are based
Term
carrying out a Simulation
Definition
  • Identify random phenomenon to be simulated
  • Describe how to simulate observations
  • Carry out simulation many times
  • Summarize results and state the conclusion
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