Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

DPT 513 > Chi Square > Flashcards

Chi Square Flashcards

1
Q

what is a commonly used observational study?

A

exposure-disease studies

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what does the contingency table record?

A

the frequency of each of the categories

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

if there are 2 categorical variables, what test are we running?

A

Chi square

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

if there are 2 continuous variables, what test are we running?

A

correlation/regression

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

if there is one categorical and one continuous variable, what tests can we run?

A

t test, WSR, MWU, ANOVA, KW, Friedman

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what variable goes into the columns?

A

the disease (DV)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what variable goes into the rows?

A

the exposure (IV)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

when data on 2 categorical characteristics are collected from one randomly selected sample, what test is run?

A

chi square

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is the key ? of interest with chi square test of independence?

A

the independence of 2 characteristics

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

t/f: contingency tables focus on the dependency/association bw column and row variables

A

true

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what is another name for the test of independence?

A

test of association

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

a PT collected data from 200 randomly selected pts. pts were asked if they had a TKA in one leg within the last 10 years and if they had contra knee pain. she wants to determine if the TKA and contra knee pain are independent.

what test should be run?
what is the H0 and Ha?

A

chi square

H0: TKA and contra knee pain are independent/not associated
Ha: TKA and contra knee pain are associated/not independent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what are the hypothesis for chi square?

A

H0: 2 categorical characteristics are independent (no association)

Ha: 2 categorical characteristics are not independent (association)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

are the hypotheses for chi square one or two sided?

A

two sided

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

how do we find X2? (don’t really need to know)

A

get the expected frequencies for each cell

calculate the o-e^2/e for each cell

add up the above values

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

if X2=6.048, df=1, p=0.014, what is the conclusion of the TKA example?

A

a chi square test of independence was performed to examine the association bw TKA and knee pain. results indicated that the association bw these variables was significant (X2(1)=6.048, p=0.014).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

how do we report chi square percentages (also not sure that we need to know this)

A

18 of 25 (72%) of pts who received a TKA w/in the past 10 years were having contra knee pain

7 of 25 (28%) of pts who didn’t receive a TKA within the past 10 years were having contra knee pain

give % of people w/ the disease and w/ or w/o the exposure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

how do we check validity of a chi square test?

A

check that all EXPECTED frequencies are greater than 5

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

if the validity check shows that some expected frequency/frequencies are less than 5, what should we do?

A

use the Fisher’s exact test values

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

are the hypotheses the same for larger contingency tables?

A

yes, they are still
H0: independent
Ha: not independent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what is relative risk?

A

how much the exposure contributes to disease

22
Q

can the chi square test tell us how much the exposure contributes to disease?

A

nope

23
Q

can relative risk be calculated with a contingency table with more than 2x2?

A

NO

24
Q

t/f: relative risk allows us to compare probabilities in terms of their ratios

A

true

25
Q

what does P[Y|X] mean?

A

the probability of Y given X

26
Q

given a normal 2x2 contingency table, what is the P[disease|exposure]?

A

a/(a+b)

27
Q

given a normal 2x2 contingency table, what is the P[disease|no exposure]?

A

c/(c+d)

28
Q

how do you calculate the RR?

A

P[disease|exposure] / P[disease|no exposure]

29
Q

if the RR=1, what does this mean?

A

the probabilities of 2 events are the same

probability of getting disease w/ or w/o exposure is the same

30
Q

if RR>1, what does this mean?

A

there is an increased risk

31
Q

if RR<1, what does this mean?

A

there is a decreased risk

32
Q

if RR=2, what does this mean in the TKA example?

A

the risk for contra knee pain is 2x as likely w/TKA than w/o TKA

33
Q

if RR=0.5, what does this mean in the TKA example?

A

the risk for contra knee pain is half as likely w/TKA than w/o TKA

34
Q

how do you calculate the RR for the probability of knee pain w/TKA?

A

P=[KP|TKA]

35
Q

how do you calculate the RR for the probability of knee pain w/o TKA?

A

P=[KP|no TKA]

36
Q

how do you calculate the RR of having knee pain?

A

[KPT|TKA] / [KP|No TKA]

37
Q

if the RR of the TKA example is 2.67, what is the conclusion?

A

the risk of having contra knee pain is 2.67 times higher for ppl who have had a TKA compared to ppl who have no had a TKA

38
Q

what is the odds ratio?

A

another way to compare 2 probabilities

the relative likelihood of a condition (disease) given a dichotomous categorical variable

ratio of odds for 2 probabilities

39
Q

t/f: odds ratio can only be used with 2x2 contingency tables

A

true

40
Q

how are odds calculated?

A

disease/no disease

41
Q

how is odds ratio calculated?

A

disease/no disease for exposed / disease/no disease for non-exposed

42
Q

why do we calculate OR?

A

to summarize difference in likelihood of disease given risk exposure

43
Q

is RR or OR the “cross ratio” of the 2x2 table?

A

OR

44
Q

what is the equation for OR?

A

OR=a/b / c/d=ad/cb

45
Q

if OR=1, what does this mean?

A

likelihood of disease is equal bw risk groups

46
Q

if OR>1, what does this mean?

A

likelihood of disease is greater in those w/risk factor

47
Q

if OR<1, what does this mean?

A

likelihood of disease is lower in those w/risk factor

48
Q

if in the TKA example, the OR is 3.05, what is the conclusion?

A

the likelihood of developing knee pain is 3.05 times greater when you have had a TKA compared to when you don’t have a TKA

49
Q

what is the difference bw OR and RR (don’t really have to know this)

A

OR is an approximation of RR

OR=RR(1-P2)/(1-P1)

50
Q

t/f: the RR and OR should be similar values

A

true

51
Q

t/f: the research question matters

A

true!

DPT 513 (9 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions