Topic 6 (statistics)

Question 1

variable

Answer 1

represented by a symbol (capital letter X,Y,A,B etc) it can take on any of a specified set of values

Question 2

sample space

Answer 2

another name for the list of all possible outcomes of an experiment is the

Question 3

random variable

Answer 3

when the value fo the variable is the outcome of an experiment the variable is called a random variable
capital letter like X are used for the random variable

Question 4

discrete random variable

Answer 4

data you can count i.e there are only certain values

probability/chance

something that can change

-to specify a discrete random variable completely = need to know its set of possible values and the probability with which it takes each one

Question 5

particular value

Answer 5

small letter such as x for a particular value of the random variable x

Question 6

probability

Answer 6

probability X is equal to a particular value of x written as P(X=x) or sometimes p(x) (notations are interchangeable)

x = particular value of X 
and P(X=x) refers to the probability that X is equal to the particular value of x

Question 7

probability distribution

Answer 7

(you can draw a table to show probability of each outcome of an experiment, this is called a probability distribution

-describes the probability of any outcome in the sample space

Question 8

probability mass function

Answer 8

probability distribution as a function = probability (mass) function

Question 9

P(X=2) = 3 x (1/5) x (4/5) squared

Answer 9

X = number of times the coins lands heads in 3 throws

3 = number of combinations nCr

(1/5) probability of tails

(4/5) squared probability of 2 heads

Question 10

rules of probability

Answer 10

• each probability positive

- sum of all probabilities equal to 1

Question 11

3
C
2

Answer 11

3 = number of throws 
2 = successful outcomes i.e 2 heads

Question 12

binomial distribution

Answer 12

must satisfy:

• fixed number of trials
• only 2 outcomes (success and failure)
• throws/events are independent
• probability of a success is constant

B(n,p)
B = binomial distribution
n = with n trials
p = probability of success is p

Question 13

p(X=x)

Answer 13

nCx p(to power of x) (1-p) (to power n-x)

Question 14

binomial cumulative distribution

Answer 14

• has to be in from x < or equal to ..

- if x> or x> or equal must change to 1 - x< or equal