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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
Q

What is power (1-B)?

A

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

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26
Q

The larger the sample size, the ______ the likelihood of detecting a difference if one truly exists.

A

greater

27
Q

How do you determine a sample size?

A
  1. minimum difference between groups deemed significant
  2. expected variation of measurement
  3. Type 1 and 2 error rates and confidence interval
28
Q

What is the p value test?

A

statistical test determine possible error rate or likelihood of chance in comparing difference or relationship between variables

29
Q

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 ______

A

chance; similar

30
Q

If the p value is ____ that the pre selected alpha value (usually 5%), then it is statistically ______

A

lower, significant

31
Q

If the p value < alpha percentage risk of error, we ____ the null hypothesis

A

reject

32
Q

What are the require assumptions of interval/ratio data?

A

normally distributed
equal variances
randomly derived and independent

33
Q

What are confidence intervals based on?

A

variation in sample

sample size

34
Q

How do you interpret a 95% confidence interval?

A

We are 95% confident that the true difference (0) or relationship (1) between the groups is contained within the confidence interval range

35
Q

If the confidence interval crosses 1.0 or 0.0 it is _______

A

not significant

36
Q

What do you always ask when reviewing the findings of a study?

A

does “statistical” significance actually confer meaningful, “clinical” significance?

37
Q

What four questions do you ask when selecting the correct statistical test?

A
  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
Q

What is correlation?

A

provides a quantitative measure of the strength and direction of a relationship between variables

39
Q

Nominal correlation test = _______ coefficient

A

contingency

40
Q

ordinal correlation test = _____ correlation

A

spearman

41
Q

interval correlation test = ______ correlation

A

Pearson

42
Q

p> .05 for a pearson correlation just means there is no ______ correlation, there still may be _______ correlations

A

linear; non-linear

43
Q

What type of data is gender?

A

nominal

44
Q

What is a survival test?

A

compares the proportions of events over time, or time to events, between groups

45
Q

What is a survival test commonly represented by?

A

kaplan-meier curve

46
Q

What are regressions?

A

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
Q

What does a chi square test do?

A

both tests compares group proportions and if they are different from that expected by chance

48
Q

Are multiple chi square test acceptable?

A

never

49
Q

What does the Bonferroni test of inequality (Bonferroni correction) do?

A

adjusts the p value for # of comparisons being made, very conservative

50
Q

What determines if a test is related/paired?

A

comparison from past to present
pre vs post
before vs after

51
Q

What do the Mann-whitney and kruskal- Wallis test do?

A

compares the median values between groups

52
Q

What does the Wilcoxon signed rank test and friendman test compare?

A

the median values between groups

53
Q

What does the student- Newman keel test do?

A

compares all pairwise comparisons possible, all groups must be equal in size

54
Q

What does the Dunnett test do?

A

compares all pairwise comparisons against a single control, all groups must be equal in size

55
Q

What does the Dunn test do?

A

compares all pairwise comparisons possible

useful when all groups are NOT equal in size

56
Q

what does a student t-test and analysis of variance (ANOVA) compare?

A

compares the means of all groups against a dependent variable

57
Q

What does an analysis of covariance (ANCOVA) do?

A

compares the means of all groups against a dependent variable while also controlling for the co variance of confounders

58
Q

What does a paired t-test and repeated measure ANOVA compare?

A

the means of all groups of related data against a dependent variable

59
Q

What does a repeated measures ANCOVA compare?

A

the means of all groups against a dependent variable while also controlling for the co variance of confounders

60
Q

What does a tukey or scheffe test compare?

A

all pairwise comparisons possible, all groups must be equal

61
Q

What is a kappa statistic?

A

a correlation test showing relationship or agreement between evaluators

62
Q

What does a +1 kappa interpretation mean?

A

the observers perfectly classify everyone the same way

63
Q

What does a 0 kappa interpretation mean?

A

there is no relationship at all between the observers classifications, above the agreement that would be expected by chance

64
Q

What does a -1 kappa interpretation mean?

A

the observers classify everyone exactly the opposite of each other

Epidemiology Exam 3 (2 decks)

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