Exam #1: Biostatistics II Flashcards
What is probability?
- Measure of the likelihood that something can happen in the future
- OR, a measure that something happened as a consequence of something else
What values can probability assume?
Values between 0 and 1
What does a value of 0 probability mean?
No chance
What does a value of 1 mean in probability?
Absolute certainty
What is the definition of “p,” probability?
times outcome occurs/ Total # of possible outcomes
*****Note that this is only used for outcomes that are random/ uncertain, not fixed or certain.
Write the equation for probability. What are the two steps to compute probability?
1) Find sample space
2) Find f(x)
p= f(x)/sample space
Answer examples 1 & 2 from the ppt presentation.
N/A
What are the definitions of an event?
1) An occurrence
2) One or more outcomes of an experiment
What is the definition of an experiment?
The act of observing or taking a measurement
What is the definition of an outcome?
The result of a measurement
In probability, how are events represented?
Uppercase letters i.e. A, B, C…etc.
What are compound events called?
Operations
What are the three types of operations?
1) Intersection= “and” operation
2) Union= “or” operation
3) Complement= “not” operation
What are disjointed events?
Two events that cannot occur simultaneously
What is the additive law in regards to disjointed events?
The probability that both events will occur is equal to the sum of the probabilities of the individual events
What is an alternative name for the additive rule?
Special rule of addition
Does the special rule of addition apply if two events are joint?
NO
What rule is used when two events are joined?
General rule of addition
What is the general rule of addition?
pA + pB - (pA + pB)
Answer 1-5 of the “thinking challenge” from the ppt.
N/A
What is the general rule of multiplication?
- If A has happened
- The probability that A and B will occur is:
- pA x pB/A
Answer the second set of “thinking challenge questions” from the ppt.
N/A
What is the special rule of multiplication?
This is the rule of multiplication to use when 2x events are INDEPENDENT
= pA x pB
Answer the example using the special rule of multiplication from the ppt.
N/A
Write Bayes’ Theorem.
N/A
What is the prior probability?
P (A) in the right hand of Bayes’ Theorem
What is the posterior probability?
P(B/A) on the left of Bayes’ Theorem
