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Evidence Based Practice > EBP2 Correlation and Reliability > Flashcards

EBP2 Correlation and Reliability Flashcards

1
Q

What kind of data does correlation and regression deal with?

A

continuous

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2
Q

What is the question to ask during correlation?

A

strength of association

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3
Q

What is the question to ask during regression?

A

strength of prediction

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4
Q

Describe correlation study.

A

pairs of scores and whether they covary

how strong is their linear relationship? what is the nature of the relationship?

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5
Q

Correlations quantify strength of what type of relationship?

A

linear

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6
Q

What is used to quantify strength of correlation?

A

correlation coefficients

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7
Q

What is the range of correlation coefficients?

A

0 and +/- 1.00

closer to 1.00 = higher strength of relationship
sign indicates direction
tighter grouping means higher coefficient

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8
Q

An r of 0.00-0.25 generally signifies what kind of relationship?

A

little or no

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9
Q

An r of 0.26-0.50 generally signifies what kind of relationship?

A

fair

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10
Q

An r of 0.51-0.75 generally signifies what kind of relationship?

A

moderate to good

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11
Q

An r of 0.75-1.00 generally signifies what kind of relationship?

A

good to excellent

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12
Q

What is the coefficient of determination?

A

square of the correlation coefficient (r^2)

is the percent of variance in y that is explained (or accounted for) by x

(amount of overlap between two circles)

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13
Q

Describe the null hypothesis and significance of coefficient.

A

null hypothesis: correlation between variables is not significantly different from zero

significance means likely not 0 in population but not strong

very sensitive to sample size

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14
Q

What is the most common type of correlation coefficient and briefly describe it?

A

pearson product-moment correlation

both variables continuous (interval or ratio)

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15
Q

What is the non-parametric analog of Pearson r and briefly describe it?

A

Spearman rank (rho) (rs)

1 continuous, 1 ordinal or 2 ordinal variables

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16
Q

What type of correlation is used when one variable is dischotomous and the other is continuous (interval or ratio)?

A

point biserial correlation (rpb)

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17
Q

True/False: Point biserial correlation has the same results as t-test.

A

true

t test will only give statistical significance where rpb also gives strength or relationship

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18
Q

Describe Rank Biserial correlation (rrb).

A

one variable is dichotomous, other is ordinal

computationally about the same as Spearman Rank

Results same as Mann-Whitney U-Test

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19
Q

What correlation is used when both variables are both dichotomous?

A

phi coefficient

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20
Q

What correlation coefficient is used when both variables are continuous?

A

pearson r

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21
Q

What correlation coefficient is used when one variable is continuous and one is ordinal?

A

spearman rho

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22
Q

What correlation coefficient is used when both variables are ordinal?

A

spearman rho

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23
Q

What correlation coefficient is used when one variable it continuous and one it nominal?

A

point biserial

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24
Q

What correlation coefficient is used when one variable is ordinal and the other is nominal?

A

rank biserial

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25
Q

What correlation coefficient is used when both variables are nominal?

A

phi coefficient

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26
Q

True/False: Correlation does not assess differences or agreement.

A

true

ICCs do

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27
Q

True/False: Causation equals correlation,

A

False - both may be caused by another factor

causation statements come from controlled experiments (RCTs)

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28
Q

True/False: Can’t generalize beyond range of scores in sample.

A

true

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29
Q

What is reliability?

A

the extent to which a measurement is consistent and free from error

a reliable measure can be expected to repeat the same score on two different occasions provided that the characteristic of interest doesn’t change

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30
Q

What is used to quantify reliability?

A

reliaility coefficients

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31
Q

What are the reliability coefficients for continuous (interval/ratio) data?

A

Pearson correlation (r)

*Intraclass correlation coefficient (ICC)

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32
Q

What are the reliability coefficients for discrete (ordinal/nominal) data?

A

Percent agreement

*Kappa

33
Q

What are the downfalls to pearson’s r reliability coefficient?

A

assesses relationship, not agreement

only two raters or occasions could be compared

so they can have perfect correlation but not agree

34
Q

What is the formula for reliability coefficients?

A

rxx = true score variability / (true score variability + error variability)

35
Q

Score _ = no reliability,

Score _ = perfect reliability

A

0, 1

36
Q

The _ the true score variability reduces reliability.

A

less

37
Q

The _ error variability, reduces reliability.

A

more

38
Q

Which of the following is not true for ICC?

a. measures degree of relationship (association) and agreement
b. can only be used with one rater or ratings
c. designed for interval/ratio
d. Often reported in conjuction with SEM

A

b - can be used with >2 raters or ratings

39
Q

ICC gives _ estimate of reliability.

SEM gives _ estimate of reliability.

A

standardized(no units), unstandardized (in units)

40
Q

What are the factors that ICC type depends on?

A

purpose of study, design of study, types of measurements taken

41
Q

ICC type is defined by two numbers in parentheses.

What position in parentheses describes the model? form?

A

first, second

42
Q

What is a model 1 for ICC?

A

each subject measured by different set of raters randomly chosen

43
Q

What is a model 2 for ICC?

A

each subject measured by same raters “randomly” chosen and representative of rater population

results are generalizable

most common for inter-rater reliability or test-retest reliability

44
Q

What is a model 3 for ICC?

A

each subject measured by same rater(s) of interest so not generalizable

most common for intra-rater reliability

45
Q

What does the form in the ICC type signify?

A

number of observations used to obtain reliability estimate

1 observation per subject rater = 1, 3=3, 4=4, etc

46
Q

What does an ICC score of > 0.90 generally mean?

A

best for clinical measurements

47
Q

What does an ICC score of >0.75 generally mean?

A

good reliability

48
Q

What does an ICC score of < 0.75 generally mean?

A

poor- moderate reliability

49
Q

ICC estimate us based on _ measures.

A

average

50
Q

True/False: ICCs should always include a 95% CI.

A

true

51
Q

In ICCs, P values tests whether point estimate is _.

A

statistically different from 0

52
Q

Describe percent agreement

A

how often raters agree 0%-100%
divide # of agreements by total of all possible agreements

based on frequency table
agreements on diagonal, disagreements are all others

53
Q

True/False: Percent agreement account for agreement due to chance.

A

false - it does not

it tends to overestimate reliability

54
Q

Describe Kappa coefficient.

A

proportion of agreement between raters after chance agreement has been removed

used on nominal and ordinal data

55
Q

Describe weighted Kappa.

A

can choose to make penalty worse for larger disagreements

weights can be arbitrary, and symmetric or asymmetric

best for ordinal data

56
Q

Generally, a kappa value of <0.4 indicates what about agreement beyond chance?

A

poor to fair

57
Q

Generally, a kappa value of 0.4-0.6 indicates what about agreement beyond chance?

A

moderate

58
Q

Generally, a kappa value of 0.6-0.8 indicates what about agreement beyond chance?

A

substantial

59
Q

Generally, a kappa value of 0.8-1.0 indicates what about agreement beyond chance?

A

excellent

60
Q

What is the most commonly applied statistical index for internal consistency?

A

cronbach’s alpha

61
Q

What is internal consistency?

A

reflection of the correlation among items and the correlation of each individual item with the total score

62
Q

True/False: Cronbach’s alpha can be used for dichotomous or ordinal (multiple choice) data.

A

true

63
Q

What is the recommended range for Cronbach’s alpha?

A

between 0.70 to 0.90

If too high, probably redundant. If too low, possibly measuring different traits

64
Q

What is response stability?

A

stability of repeated measures over time

~test-rest reliability

65
Q

What are the three commonly used statistical methods to express response stability?

A

Standard error of measurement, Minimal detectable difference/chance, coefficient of variation

66
Q

What is the standard error of measurement?

A

measure of reliability using standard deviation of the measurement errors
SD x square root of 1-ICC

can be used to create a 95% CI around a measurement (95% CI = Score +- 1.96(SEM)

67
Q

What is minimal detectable difference?

A

amount of change in a variable that must be achieved to reflect a true change/difference

mathematical multiple of SEM

MDC = mean +- (1.06)(SEM)(sqrt2)

68
Q

What is coefficient of variation?

A

ratio of SD to mean, expressed as percentage

CV = (SD/mean) x 100

69
Q

What are alternate forms?

A

comparing different methods of testing same phenomenon with different instruments

70
Q

What is Limits of Agreement?

A

range that includes ~ 95% of differences

95%LOA = X +- 2s

71
Q

Describe a Bland-Altman plot.

A

spread of scores around a 0 point to help decide if the observed error is acceptable if we substitute one measurement method for another

If all on one side of 0, consistently measuring more

tighter range = more agreement

72
Q

What question does correlation seek to answer?

A

Is there a strength in the association between variables?

73
Q

True/False: You are reading a study that has shown a strong correlation between hours studying (greater than 3 hours) for an EBP II exam and getting a 90% or above (r = .94). We can now infer that studying for 3 or more hours will cause one to get a 90% or above on the exam.

A

False - correlation does not equal causation

74
Q

ICCs are primarily used with dichotomous or categorical data.

A

continuous data (ratio/interval)

75
Q

You are wanting to use a reliability process that is the most conservative approach. What would be most appropriate if this were your goal?

A

model 1 ICC

76
Q

You are reading a study that is reporting ICC values and note that the following was reported “ICC(2,1)”. What does this tell the reader?

A

Each subject measured by same raters using an inter-rater approach where only one observation per subject per rater was performed.

77
Q

You are wanting to assess for the percentage of between raters who are performing the Lachman’s test on those suspected of an ACL tear. The raters are rating their findings as either positive or negative. What would most appropriately assist with this?

A

Kappa

78
Q

You come across a Kappa value of .54. How would you interpret the magnitude of this value?

A

moderate agreement

79
Q

True/False: SEM is a measurement that takes into account ICC.

A

true

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