Exam #1: Biostatistics II

Question 1

What is probability?

Answer 1

• Measure of the likelihood that something can happen in the future
• OR, a measure that something happened as a consequence of something else

Question 2

What values can probability assume?

Answer 2

Values between 0 and 1

Question 3

What does a value of 0 probability mean?

Answer 3

No chance

Question 4

What does a value of 1 mean in probability?

Answer 4

Absolute certainty

Question 5

What is the definition of “p,” probability?

Answer 5

times outcome occurs/ Total # of possible outcomes

*****Note that this is only used for outcomes that are random/ uncertain, not fixed or certain.

Question 6

Write the equation for probability. What are the two steps to compute probability?

Answer 6

1) Find sample space
2) Find f(x)

p= f(x)/sample space

Question 7

Answer examples 1 & 2 from the ppt presentation.

Answer 7

N/A

Question 8

What are the definitions of an event?

Answer 8

1) An occurrence

2) One or more outcomes of an experiment

Question 9

What is the definition of an experiment?

Answer 9

The act of observing or taking a measurement

Question 10

What is the definition of an outcome?

Answer 10

The result of a measurement

Question 11

In probability, how are events represented?

Answer 11

Uppercase letters i.e. A, B, C…etc.

Question 12

What are compound events called?

Answer 12

Operations

Question 13

What are the three types of operations?

Answer 13

1) Intersection= “and” operation
2) Union= “or” operation
3) Complement= “not” operation

Question 14

What are disjointed events?

Answer 14

Two events that cannot occur simultaneously

Question 15

What is the additive law in regards to disjointed events?

Answer 15

The probability that both events will occur is equal to the sum of the probabilities of the individual events

Question 16

What is an alternative name for the additive rule?

Answer 16

Special rule of addition

Question 17

Does the special rule of addition apply if two events are joint?

Answer 17

NO

Question 18

What rule is used when two events are joined?

Answer 18

General rule of addition

Question 19

What is the general rule of addition?

Answer 19

pA + pB - (pA + pB)

Question 20

Answer 1-5 of the “thinking challenge” from the ppt.

Answer 20

N/A

Question 21

What is the general rule of multiplication?

Answer 21

• If A has happened
• The probability that A and B will occur is:
• pA x pB/A

Question 22

Answer the second set of “thinking challenge questions” from the ppt.

Answer 22

N/A

Question 23

What is the special rule of multiplication?

Answer 23

This is the rule of multiplication to use when 2x events are INDEPENDENT

= pA x pB

Question 24

Answer the example using the special rule of multiplication from the ppt.

Answer 24

N/A

Question 25

Write Bayes’ Theorem.

Answer 25

N/A

Question 26

What is the prior probability?

Answer 26

P (A) in the right hand of Bayes’ Theorem

Question 27

What is the posterior probability?

Answer 27

P(B/A) on the left of Bayes’ Theorem