Stats & Probability

Question 1

Independent/dependent probability

Answer 1

Multiply

Question 2

Combination

Answer 2

Order does not matter

nCr= n!/r!(n-r)!

Question 3

Permutation

Answer 3

Order matters

nPr= n!/(n-r)!

Question 4

Mutually exclusive probability

Answer 4

Add probabilities

Question 5

Variance

Answer 5

Find the mean
Subtract mean from each data pt and square
Find mean of squared differences

Question 6

Standard deviation

Answer 6

Take square root of variance

Variance:Find mean, subtract mean from each data pt and square, find mean of squared differences

Question 7

Correlation coefficient

Answer 7

-1 maximum negative relationship
0 no relationship
1 maximum positive correlation

Question 8

Stratified random sample

Answer 8

Population divided into similar groups then simple random sample chosen from each group
… Class divided into boys and girls and two students chosen from each group

Question 9

Systematic random sample

Answer 9

Member chosen at regular intervals

… Every third student

Question 10

Cluster Sampling

Answer 10

Population divided into clusters then a number of clusters are selected as sample
… Randomly select hospitals (first stage) then interview OR nurses at 1 or 2 hospitals

Question 11

Probability at least one event will occur

Answer 11

1-P(neither event occurs)

Question 12

Standard deviation rules

Answer 12

Normal 1 standard deviation 68%
2 standard deviations 95%
3 standard deviations 99%

5% does not fall within 2 standard deviations

Question 13

z score

Answer 13

of standard deviations from mean

x-mean)/(standard deviation

Question 14

Binomial probability

Answer 14

nCr * p^r * q^n-r

n=#trials
r=specific events you want
p=probability event will occur
q=probability event will not occur