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Epidemiology Exam 3 > Introduction to Biostatistics in Epidemiology > Flashcards

Introduction to Biostatistics in Epidemiology Flashcards

1
Q

What are the three notes about human studies?

A
  1. Data will be collected on desired variables
  2. Comparisons are commonly made
  3. inferences will be made about the sample derived data and their comparisons
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2
Q

What is a null hypothesis?

A

research perspective which states there will be no (true) difference between the groups being compared

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3
Q

What are the 3 key attributes of data measurement?

A
  1. order/magnitude
  2. consistency of scale/ equal distances
  3. rational absolute zero
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4
Q

What are the 3 levels of data?

A

nominal
ordinal
interval or ratio

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5
Q

Describe nominal data

A

named categories
no order or magnitude
no consistency of scale or equal distances
simply labeled variables without quantitative characteristics (or dichotomous/binary)

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6
Q

Describe ordinal data

A

ordered
yes order and magnitude
no consistency of scale or equal distances

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7
Q

Describe interval/ratio data

A

interval: arbitrary zero value
ratio: absolute zero value
yes order and magnitude
yes consistency of scale or equal distances

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8
Q

After data is collected, we can appropriately go _____ in specificity/detail of data measurement, but never ____

A

down; up

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9
Q

What is variance?

A

the average of the squared differences in each individual measurement value and the groups mean

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10
Q

What is standard deviation?

A

square root of variance value

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11
Q

Graphical representation shows ____ of data

A

Shape

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12
Q

Normally distributed= _______

A

symmetrical

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13
Q

What are stats test useful for normally distributed data called?

A

parametric test

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14
Q

Describe a positively skewed graph.

A

asymmetrical distribution with one tail longer than another

mean is higher than median (tail points to right)

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15
Q

A distribution is skewed anytime when __________

A

median differs from the mean

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16
Q

Describe a negatively skewed graph

A

asymmetrical distribution with one tail longer than the other
mean is lower than median (tail points to left)

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17
Q

What is skewness?

A

a measure of asymmetry of a distribution

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18
Q

What is kurtosis?

A

a measure of the extent to which observations cluster around the mean

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19
Q

What is positive kurtosis?

A

more cluster

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20
Q

What is negative kurtosis?

A

less cluster

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21
Q

What are the required assumptions of interval/ratio data?

A
  1. normally distributed
  2. equal variances
  3. randomly derived and independent
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22
Q

How do you handle data that is not normally distributed?

A
  1. use a statistical test that does not require the data to be normally distributed (non parametric test)
  2. transform data to a standardized value ( z score or log transformation)
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23
Q

What is a type 1 error?

A

Not accepting the null hypothesis when it is actually true, and you should have accepted it, false positive

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24
Q

What is a type 2 error?

A

Accepting the null hypothesis when it is actually false, and you should have not accepted it, false negative

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25
What is power (1-B)?
the statistical ability of a study to detect a true difference, if one truly exist between group comparisons and therefore the level of accuracy in correctly accepting or not accepting the null hypothesis
26
The larger the sample size, the ______ the likelihood of detecting a difference if one truly exists.
greater
27
How do you determine a sample size?
1. minimum difference between groups deemed significant 2. expected variation of measurement 3. Type 1 and 2 error rates and confidence interval
28
What is the p value test?
statistical test determine possible error rate or likelihood of chance in comparing difference or relationship between variables
29
A p value is obtained, based on the probability of observing, due to _______ alone, a test statistic value as extreme or more extreme than actually observed if groups were ______
chance; similar
30
If the p value is ____ that the pre selected alpha value (usually 5%), then it is statistically ______
lower, significant
31
If the p value < alpha percentage risk of error, we ____ the null hypothesis
reject
32
What are the require assumptions of interval/ratio data?
normally distributed equal variances randomly derived and independent
33
What are confidence intervals based on?
variation in sample | sample size
34
How do you interpret a 95% confidence interval?
We are 95% confident that the true difference (0) or relationship (1) between the groups is contained within the confidence interval range
35
If the confidence interval crosses 1.0 or 0.0 it is _______
not significant
36
What do you always ask when reviewing the findings of a study?
does "statistical" significance actually confer meaningful, "clinical" significance?
37
What four questions do you ask when selecting the correct statistical test?
1. What data level is being recorded? 2. what type of comparison/assessment is desired? 3. How many groups are being compared? 4. is the data independent or related (paired)?
38
What is correlation?
provides a quantitative measure of the strength and direction of a relationship between variables
39
Nominal correlation test = _______ coefficient
contingency
40
ordinal correlation test = _____ correlation
spearman
41
interval correlation test = ______ correlation
Pearson
42
p> .05 for a pearson correlation just means there is no ______ correlation, there still may be _______ correlations
linear; non-linear
43
What type of data is gender?
nominal
44
What is a survival test?
compares the proportions of events over time, or time to events, between groups
45
What is a survival test commonly represented by?
kaplan-meier curve
46
What are regressions?
provide a measure of the relationship between variables by allowing the prediction about the dependent, or outcome, variable knowing the value/category of independent variables
47
What does a chi square test do?
both tests compares group proportions and if they are different from that expected by chance
48
Are multiple chi square test acceptable?
never
49
What does the Bonferroni test of inequality (Bonferroni correction) do?
adjusts the p value for # of comparisons being made, very conservative
50
What determines if a test is related/paired?
comparison from past to present pre vs post before vs after
51
What do the Mann-whitney and kruskal- Wallis test do?
compares the median values between groups
52
What does the Wilcoxon signed rank test and friendman test compare?
the median values between groups
53
What does the student- Newman keel test do?
compares all pairwise comparisons possible, all groups must be equal in size
54
What does the Dunnett test do?
compares all pairwise comparisons against a single control, all groups must be equal in size
55
What does the Dunn test do?
compares all pairwise comparisons possible | useful when all groups are NOT equal in size
56
what does a student t-test and analysis of variance (ANOVA) compare?
compares the means of all groups against a dependent variable
57
What does an analysis of covariance (ANCOVA) do?
compares the means of all groups against a dependent variable while also controlling for the co variance of confounders
58
What does a paired t-test and repeated measure ANOVA compare?
the means of all groups of related data against a dependent variable
59
What does a repeated measures ANCOVA compare?
the means of all groups against a dependent variable while also controlling for the co variance of confounders
60
What does a tukey or scheffe test compare?
all pairwise comparisons possible, all groups must be equal
61
What is a kappa statistic?
a correlation test showing relationship or agreement between evaluators
62
What does a +1 kappa interpretation mean?
the observers perfectly classify everyone the same way
63
What does a 0 kappa interpretation mean?
there is no relationship at all between the observers classifications, above the agreement that would be expected by chance
64
What does a -1 kappa interpretation mean?
the observers classify everyone exactly the opposite of each other

Epidemiology Exam 3 (2 decks)

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