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Epidemiology > Exam 3 : Biostatistics > Flashcards

Exam 3 : Biostatistics Flashcards

1
Q

A research perspective which states there will be NO difference between the groups being compared

A

Null hypothesis

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2
Q

What are the three primary level for variables based on answering 2 key attributes in stats?

A

Nominal
Ordinal
Interval or ratio

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3
Q

That are the three key attributes of data measurment?

A
  1. Order/ magnitude
  2. Consistency of scale/ equal distances
  3. Rational absolute zero
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4
Q

What level of measurement can be described as dichotomous/ binary; Non-ranked named categories?

A

Nominal

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5
Q

What level of measurement can be described as Ordered, rank-able categories; non-equal distance?

A

Ordinal

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6
Q

What level of measurement can be described as having order & magnitude & equal distances?

A

Interval/ ratio

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7
Q

Which of the two, interval or ratio, has an arbitrary zero value ( 0 doesnt mean absence)

A

Interval

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8
Q

Which of the two, interval or ratio, has an absolute zero value? ( o means absence of measurment value)

A

Ratio

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9
Q

T/F

After data is collected, we can appropriately go up in specificity/ detail of data measurements, but not down.

A

False

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10
Q

What is descriptive statistics?

A

Non-comparative, simple description of various elements of the study’s data such as : Age, education, living situation, native, number of people..ext..

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11
Q

The average of the squared-differences in each individual measurement value and the groups’ mean is what calculation? (From mean)

A

Variance

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12
Q

The square root of variance value is what calculation?

A

Standard deviation

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13
Q

T/F

Normally distributed graphical data is what symmetrical

A

True

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14
Q

What do the mean/ median/ mode look like in a normally distributed dataset?

A

Equal/ near equal

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15
Q

What are stats test useful for normally-distributed data called?

A

Parametric tests

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16
Q

What are parameters?

A

Mean/ median/ mode

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17
Q

1 standard deviation on both sides of the mean (up and down) is approximately what percentage?

A

68%

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18
Q

2 standard deviations on both sides of the mean is approximately what percentage?

A

95%

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19
Q

3 standard deviations on both sides of the mean are approximately what percentage?

A

99.7%

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20
Q

What data NEEDS to be normally distributed?

A

Interval

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21
Q

When the mean is higher than median what type of skew does this make?

A

Positive skew

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22
Q

What does “skew” mean graphically?

A

The graph represents an asymmetrical distribution with one ‘tail’ longer than the other

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23
Q

When the mean is lower than the median the graphical data is known as what?

A

Negatively skewed

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24
Q

When the tail is on the left what type of skew is this?

A

Negative skew

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25
Q

When the tail is on the right, what type of skew is this?

A

Positive skew

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26
Q

Outlier can move the mean, median, mode?

A

Mean

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27
Q

What is a skewness value?

A

A measure of the asymmetry of a distribution

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28
Q

What does a graph with a skewness value of zero look like?

A

Evenly distributed

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29
Q

What would a graph with -2.0 skewness value look like?

A

Negative skew, so tail on left

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30
Q

What is known as the measure of the extent to which observations cluster around the mean?

A

Kurtosis

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31
Q

When the kurtosis value is 0, what does the graph look like?

A

Normally distributed

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32
Q

What does a positive kurtosis imply

A

More clusters

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33
Q

What does a negative kurtosis imply?

A

Less clusters

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34
Q

What data would be considered discrete?

A

Nominal

Ordinal

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35
Q

What data would be considered continuous?

A

Interval

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36
Q

What test tell us if interval data is normally distributed/ of equal variances between the groups?

A

Levene’s test

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37
Q

What do we do when data is NOT normally-distributed?

A
  1. Use statistical test that doesn’t require parametric test (non parametric tests)
  2. Transform data to a standardized value ( z-score or log)
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38
Q

What do we always run, even if the data isn’t normally distributed?

A

Descriptive statistics & graphs

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39
Q

What error is it when the researcher rejects the null hypothesis when it is actually TRUE?

A

Type 1 error ( alpha error)

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40
Q

What error is it when the researcher accepts the null hypothesis when it is actually FALSE?

A

Type 2 error ( beta error)

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41
Q

The statistical ability of a study to detect a true difference, IF one truly exists between group-comparisons. The larger the sample size, the greater likelihood hood. What is this?

A

Power

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42
Q

T or F

The smaller the difference between groups necessary to be considered “significant”, the greater sample size needed.

A

True

43
Q

What are the three sample size determiners?

A
  1. Minimum difference between groups deemed significant
  2. Expected variation of measurment
  3. Type 1 & 2 error rates & confidence intervals
44
Q

What are the steps to getting a p value?

A
  1. Critical value calculated
  2. Compared to appropriate table of probabilities
  3. Probability value is obtained
45
Q

T or F

P value is based on the probability of observing, due to chance alone, a test statistic value as extreme or more extreme than actually observed if groups were similar

A

True

46
Q

T/ F

P value is picked after the study is run

A

False

47
Q

When is p value statistically significant?

A

When it is lower than the picked value (5%)

48
Q

If the p value is lower than the preselected p value, making the information statistically significant, then what do we do with the null hypothesis?

A

Reject the null

49
Q

What are 4 interpretations of a pre-set (a priori) p value?

A
  1. Probability of Type 1 error
  2. Probability of erroneously claiming a difference
  3. Probability of obtaining group differences as great or greater if the groups were actually the same/equal
  4. Probability of obtaining a test statistic as high/higher if the groups were actually the same/equal
50
Q

What are the 3 required assumptions of interval/ratio data?

A
  1. Normally distributed
  2. Equal variances
  3. Randomly-derived & independent
51
Q

What are the most common selections for a confidence interval?

A

90%
95%
99%

52
Q

What are the two things that confidence intervals are based on?

A
  1. Variation in sample

2. Sample size

53
Q

T/F

If we hope over 1.0 in the confidence interval ( go from neg to pos) then it is statistically significant

A

False ( if it crosses over 1.0, it ISN’T statistically significant)

54
Q

What does a 95% confidence interval mean?

A

We are 95% confident that the “true” difference or relationship between the groups is contained within the confidence interval range

55
Q

T/F

Statistical significance doesn’t confer meaningful clinical significance

A

True, it doesn’t. Statistical significance really has no magnitude, it only tells us that there is or isn’t a probability of a difference between groups

56
Q

What is the first key question when determining the correct statistical test?

A

What data level is being recorded?

  • order/ magnitude
  • equal, consistent distances
57
Q

What is the second question to ask to correctly select a statistical test?

A
  1. What type of comparison/assessment is desired?
    - correlation
    - event/occurrence/ time to event
    - outcome prediction/ association (OR)
    - frequencies/counts/proportions
58
Q

What is the third question to ask to correctly select a statistical test?

A
  1. How many groups are being compared

- 2 0r 3

59
Q

What is the 4th question to ask to select the correct statistical test?

A
  1. Is the data independent or related?
60
Q

This test provides a quantitative measure of the strength (magnitude) & direction of a relationship between variables

A

Correlation

61
Q

What is the nominal correlation test?

A

Contingency coefficient

62
Q

What is the ordinal correlation test?

A

Spearman correlation

63
Q

What is the interval correlation test?

A

Pearson correlation

64
Q

Greater than 5% for a Pearson correlation just means there is no linear correlation; what may still be present though?

A

Non-linear correlation

65
Q

This correlation test controls for confoundings

A

Partial correlation

66
Q

What happens when a p value is greater than 5%?

A

It’s not linear

67
Q

What is the time to event/ event occurrence test ?

A

Survival test

68
Q

This test compares the proportion of events over time, or time to events, between groups

A

Survival test

69
Q

What is a nominal survival test?

A

Log-rank test

70
Q

What is the ordinal survival test?

A

Cox-proportional hazards test

71
Q

What is the interval survival test?

A

Kaplan-Meier test

72
Q

How can we represent all survival tests graphically?

A

By a Kaplan Meier curve

73
Q

What is the outcome PREDICTION/ association test?

A

Regression

74
Q

This test provides a measure of the relationship between variables by allowing the prediction about the dependent, or outcome, variable knowing the value/category of independent variables
-also able to calculate OR for a measure of association

A

Regression

75
Q

What is the nominal regression test?

A

Logistic regression

76
Q

What is the ordinal regression test?

A

Multinomial logistic regression

77
Q

What is the interval regression test?

A

Linear regression

78
Q

For nominal data of greater than 5 cell counts and 2 or more groups, what test should we use?

A

Chi square

79
Q

For nominal data of less than 5 cell counts and 2 or 3 groups what test should we use?

A

Fisher’s exact test

80
Q

T/F
For statistically significant findings in nominal data of 3 or more comparisons, one must perform subsequent analysis to determine which groups are different

A

True

81
Q

What subsequent tests should be run on a nominal data that 3 or more comparisons are found to be statistically significant?

A

Bonferroni test of inequality

Bonferroni correction

82
Q

This test adjusts the p value for number of comparisons being made. It is very conservative

A

Bonferroni test of inequality

83
Q

When using nominal related data in 2 groups, what test should we run?

A

McNemar test

84
Q

When using nominal related data in 3 or more groups, what test should we use?

A

Cochran

85
Q

When using ordinal independent data in 2 groups, what test should we run?

A

Mann-Whitney test

86
Q

When using ordinal independent data in 3 or more groups, what test should we use?

A

Kurskal-Wallis test

87
Q

When running a Kruskal Wallis test, when 3+ group comparisons are significant then we must perform a ______________ to determine where differences are.

A

Post-hoc test

88
Q

When using ordinal paired data of 2 groups, what test do we run?

A

Wilcoxon signed rank test

89
Q

When using ordinal paired data with 3 or more groups, what test should we run?

A

Friedman test

90
Q

What are 3 post hoc tests for 3 or more group comparisons in ordinal data?

A

Student Newman Keul Test
Dunnett test
Dunn test

91
Q

Which post hoc test compares all to a single control

A

Dunnett test

92
Q

What post hoc test compares all possible comparisons and the groups must be equal in size?

A

Student Newman Keul test

93
Q

What post hoc test compares all comparisons possible but the groups are not of equal size?

A

Dunn test

94
Q

When using independent interval data from 2 groups, what test should we run?

A

Student t-test

95
Q

When using independent interval data from 3 or more groups, what tests should we run?

A

ANOVA

MANOVA

96
Q

T/F

ANOVA test compares the means of all groups against a single DV

A

True

97
Q

T/F

MANOVA test compares the means of all groups against multiple DVs?

A

True

98
Q

When using related interval data from 2 groups, what test should we run?

A

Paired t test

99
Q

When using related interval data from 3 or more groups, what tests should we run?

A

ANOVA

MANOVA

100
Q

T/F

Turkey test is a post hoc test for interval dat that is slightly more conservative then the Stu.N.K test.

A

True

101
Q

T/F
The scheffe test is a post hoc test for interval data that is less affected by violations informality and homogeneity of variances. It is considered the most conservative.

A

True

102
Q

This correlation test shows relationship or agreement between evaluators (consistency of decisions, determinations)

A

Kappa statistics

103
Q

what does a kappa test of +1 mean?

A

The observers perfectly classify everyone exactly the same way

104
Q

What does a kappa test of 0 mean?

A

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

Epidemiology (9 decks)

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