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1
Q

what is cohens Kappa statistic?

A

measure of agreement between raters for categorical measures

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2
Q

there are two different types of agreement dependant on which data types?

A

continous

categorical

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3
Q

equivalent of kappas for continous data?

A

Intraclass correlation (ICC)

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4
Q

is agreement the same as correlation?

A

no

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5
Q

which plot can be used to calculate the means and differences between two techniques?

A

Bland-Altman method

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6
Q

Kappa and weighteed kappa is used for which type of data set?

A

categorical ratings

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7
Q

ICC and bland altman is used for which type of data set?

A

continuous

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8
Q

when are repeated measures seen?

A

measuring same experimental unit on several occasions

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9
Q

give examples of repeated measures?

A

glucose uptake by cells at different time points

cholesterol in RCT of new statin at 3,6 and 12 months

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10
Q

what test is commonly used when analysing repeated measures?

A

t-tests

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11
Q

multiple testing when analysing repeated measureshas what effect on error?

A

increases type I error

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12
Q

how is the inc in type I error with multiple testing accounted for?

A

adjustign p-value

Bonferoni correction

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13
Q

why is bonferoni correction necessary?

A

multiple tests assumes aim of study is to show sig difference at every time point but most studies aim to show overall effect

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14
Q

how would you describe the primary hypothesis when dealing with overall analysis of repeated measures?

A

primary hypothesis os global

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15
Q

what is ANOVA?

A

Analysis of Variance

determines whether there are any statistically significant differences between the means of 3 or more unrelated groups

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16
Q

what is sphericity?

A

refers to teh issue of similarity of variances in the differences between treatments

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17
Q

when sphericity is not met what can be used as an alternative to the correction factors?

A

MANOVA

has less power than repeated measures analysis so generally avoided

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18
Q

what can be used in addition to MANOVA if spherivity is not met?

A

Greenhouse-Geisser

Huynh-Feldt adjustment

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19
Q

what are parametric tests?

A

involve estimating parameters such as the mean and assumes that distribution of sample means are normally ditributed

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20
Q

what is skewness?

A

skewed distributions i.e. postive or negative

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21
Q

if distribution is skewed what can be done to normalise data?

A

use log

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22
Q

what are non-parametric tests?

A

tests for situations where nothign is assumed about the distribution

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23
Q

Non-parametric tests are sometimes called?

A

Distribution free tests

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24
Q

what is a practical difference between parametric and non-parametric methods?

Study These Flashcards
A

NP mehtods use ranks of values rather than actual values

25
what is the median?
value above and below which 50% of the data lie
26
in symmetric distributions the median and the mean are the same true/false?
true
27
in skewed distributions which is more appropriate the median or the mean?
the median
28
what is a T-test?
used to test whether the mean of a sample is significantly different from another relies on sample being drawn from a normally distributed population
29
if a sample is not normal what can be used instead of a t-test?
Wilcoxin Signed Rank Test
30
what is the difference between teh Wilcoxin signed rank and the Wilcoxin Rank sum?
Signed Rank= paired t-test Rank Sum= independant t-test
31
give an advantage and a disadvantage of a paired t-test?
advantage= uses all detail of available data- most powerful test if data normally distributed disadvantage= assumes data are a random sample from a population which is norally distributed
32
describe paired and not paired comparisons
paired- same sample measured on 2 diff occasions not-paired- two independant samples ('matched' samples by age/gender are paired)
33
what is another name for the Wilcoxin Rank Sum?
Mann-Whitney test
34
when is the Mann whitney test used?
used when you want to compare two unrelated or INDEPENDANT groups
35
what assumptions does the Mann Whitney have?
distributions have similar shape but need not be normal can be used for small/large sample sizes
36
what is the spearman rank correlation?
tests monotonic relationship between 2 measured variables lies between -1 to +1
37
a spearman rank correlation close to 0 is strong/weak?
weak or no correlation
38
when is Chi-squared testing used?
when comparing 2 or more groups of categorical or nominal data (as opposed ot measured data)
39
when comparing 3 or more groups and data is not normal what is used when independant and related samples?
independant sample= Kruskal-Wallis related samples= Friedman
40
what are survival regression models?
risk of event (mortality) in next time interval t, conditional to having survued to start of interval t (expressed in terms of hazard function)
41
what is hazard?
hazard rate is an instantaneous rate of events as a function of time
42
which model expresses the relationship between the hazard and a set of variables or covariates?
The cox model
43
what is hazard ratio?
ratio of hazards (HR) in two groups e.g. men v women (it is the improvement of one group over the other)
44
what happens to the HR over time?
stays constant
45
explain the following hazard ratios: HR= 1, HR= \<1, HR= \>1
HR= 1 do not reject null hypothesis (i.e. no difference) HR= \<1 reduction in hazard relative ot comparator i.e 0.6 is 40% reduction HR= \>1 increase in hazard relative to comparator i.e. 1.7 is 70% increase
46
what is the logrank test? is it parametric or nonparametric
a hy[pothesis test used to compare survival distributions of two samples
47
if a 95% CI for a HR included 1 can you reject the null hypothesis?
no
48
how is hazard ratio interpretated for continuous and categorical variables?
continous i.e. age- HR represents inc per unit in age categorical i.e. dukes staging- HR represents inc per category
49
when is multiple regression modelling used?
to asses relationship between two variables whilst allowing for another variable
50
what is a cofounder?
factor which is related to both the variable of interest and the outcome
51
give two examples of selection criteria used when model has many variables?
Alaike's Information Criterion (AIC) Schwarts's Bayesian Information Criterion (BIC)
52
multipe regression models are the most used analytical tool in which type of research?
quantitive research
53
define correlation
strength of the linear relationshop between two variables
54
what is regression analysis?
determines nature of a relationship i.e. is there a relationship between alcohol units drank and liver cirrhosis
55
what is pearsons coefficient of correlation?
measures the strength of the linear relationship between one dependant and one independant variable
56
what are the values of pearsons coefficient?
r= +1 positive correlation r= -1 negative correlation r= 0 no linear relationship
57
define residual
a residual is teh difference betwween the predicted value (fitted line) and the actual value or unexplained variation
58
what is a durbin watson test?
test for autocorrelation in the residuals from a statistical regression analysis

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