Probability and Statistics

Question 1

2 ways a study can screw the pooch

Answer 1

caused by chance (random error)

not caused by chance (bias or systematic error)

Question 2

what deals with random errors

Answer 2

statistical inference

Question 3

T/F random errors bias a study

Answer 3

false

may be wrong but not biased

Question 4

what is a systematic error

Answer 4

error that is inherent to the study method being used and results in a predictable and repeatable error for each observation

Question 5

T/F systemic errors bias a study

Answer 5

true

Question 6

T/F there is a formal method to deal with systematic errors

Answer 6

false

Question 7

tests of statistical inference

Answer 7

estimate the likelihood that a study result was caused by chance

Question 8

T/F statistically significant means clinically important or meaningful

Answer 8

false

Question 9

what is a chance occurrence

Answer 9

something that happen unpredictably without discernible human intention or with no observable cause

Question 10

random variation

Answer 10

there is error in every measurement

if measure something over an over again will get slight variations in measurements

Question 11

what does statistical inference tell us

Answer 11

if we measure something only once, how sure are we that our measurement has been caused by chance

Question 12

what 2 methods are used to estimate random variation in a study

Answer 12

confidence intervals

p-values

Question 13

T/F width of the CI is related to sample

Answer 13

true

• small samples have large CI
• large samples have small CI

Question 14

T/F if the 95% CI for the OR does not include one the OR is statistically significant

Answer 14

true

Question 15

T/F the same rules apply for OR, PR, RR when it comes to CI

Answer 15

true

if CI spans one they are statistically insignificant and there is no association

Question 16

what do P-values estimate

Answer 16

whether a measured association was likely to have been caused by chance

Question 17

Does P-value give you information on size of sample and range of true value

Answer 17

it sure as shit doesn’t

Question 18

to be statistically significant p-value must be less than

Answer 18

0.05

Question 19

how do you calculate p-value

Answer 19

chi-squared test

student’s T-test

correlation

Question 20

null hypothesis

Answer 20

hypothesis of no association

Question 21

alternative hypothesis

Answer 21

the research question

there is an association between exposure and disease

Question 22

T/F we use p-values or CIs accept or reject the null hypothesis

Answer 22

true

Question 23

wha is a type 1 error

Answer 23

false positive

• reject the null when it is not false
• saying there is an association when there isn’t

Question 24

what is a type II error

Answer 24

false negative

• not rejecting the null when it is false
• saying there is no association when there is

Question 25

types of data

Answer 25

categorical

continuous

Question 26

categorical data

Answer 26

broken into discrete categories

• nominal
• ordinal

Question 27

continuous data

Answer 27

variable is numeric and can have any one of many possible values

Question 28

nominal

Answer 28

named, not ordered

horse vs. donkey; stallion vs. gelding vs mare vs colt vs filly

Question 29

ordinal

Answer 29

named ad ordered by nor constant value between ranks

neonate vs juvenile vs adult vs geriatric

Question 30

describe categorical data

Answer 30

frequency distribution

may be represented as a table or bar chart

statistical test

Question 31

describe continuous data

Answer 31

frequency distribution and histogram

describe the center of the distribution

describes the amount of dispersion

describe the shape of distribution

statistical tests

Question 32

what is central tendency

Answer 32

describes the center of the distribution

mean, median, mode

Question 33

what is dispersion (spread)

Answer 33

describes how closely the values are gathered around the center of distribution
range, standard deviation

Question 34

Chi-squared test

Answer 34

test of independence between 2 categorical variables

p-value

used for categorical data

Question 35

student’s T-test

Answer 35

difference in means
compare averages of 2 groups
used for continuous data

H0=means of 2 groups are the same

Ha= can be one or two tailed

Question 36

correlation

Answer 36

measures the strength and direction of a linear relationship between 2 continuous variables

Question 37

correlation coefficient (r)

Answer 37

often used for dose response relationships

both variables are numerical, usually continuous

• strong: r>0.80
• weak: r