Exam 3 : Biostatistics Flashcards
1
Q
A research perspective which states there will be NO difference between the groups being compared
A
Null hypothesis
2
Q
What are the three primary level for variables based on answering 2 key attributes in stats?
A
Nominal
Ordinal
Interval or ratio
3
Q
That are the three key attributes of data measurment?
A
- Order/ magnitude
- Consistency of scale/ equal distances
- Rational absolute zero
4
Q
What level of measurement can be described as dichotomous/ binary; Non-ranked named categories?
A
Nominal
5
Q
What level of measurement can be described as Ordered, rank-able categories; non-equal distance?
A
Ordinal
6
Q
What level of measurement can be described as having order & magnitude & equal distances?
A
Interval/ ratio
7
Q
Which of the two, interval or ratio, has an arbitrary zero value ( 0 doesnt mean absence)
A
Interval
8
Q
Which of the two, interval or ratio, has an absolute zero value? ( o means absence of measurment value)
A
Ratio
9
Q
T/F
After data is collected, we can appropriately go up in specificity/ detail of data measurements, but not down.
A
False
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..
11
Q
The average of the squared-differences in each individual measurement value and the groups’ mean is what calculation? (From mean)
A
Variance
12
Q
The square root of variance value is what calculation?
A
Standard deviation
13
Q
T/F
Normally distributed graphical data is what symmetrical
A
True
14
Q
What do the mean/ median/ mode look like in a normally distributed dataset?
A
Equal/ near equal
15
Q
What are stats test useful for normally-distributed data called?
A
Parametric tests
16
Q
What are parameters?
A
Mean/ median/ mode
17
Q
1 standard deviation on both sides of the mean (up and down) is approximately what percentage?
A
68%
18
Q
2 standard deviations on both sides of the mean is approximately what percentage?
A
95%
19
Q
3 standard deviations on both sides of the mean are approximately what percentage?
A
99.7%
20
Q
What data NEEDS to be normally distributed?
A
Interval
21
Q
When the mean is higher than median what type of skew does this make?
A
Positive skew
22
Q
What does “skew” mean graphically?
A
The graph represents an asymmetrical distribution with one ‘tail’ longer than the other
23
Q
When the mean is lower than the median the graphical data is known as what?
A
Negatively skewed
24
Q
When the tail is on the left what type of skew is this?
A
Negative skew
25
When the tail is on the right, what type of skew is this?
Positive skew
26
Outlier can move the mean, median, mode?
Mean
27
What is a skewness value?
A measure of the asymmetry of a distribution
28
What does a graph with a skewness value of zero look like?
Evenly distributed
29
What would a graph with -2.0 skewness value look like?
Negative skew, so tail on left
30
What is known as the measure of the extent to which observations cluster around the mean?
Kurtosis
31
When the kurtosis value is 0, what does the graph look like?
Normally distributed
32
What does a positive kurtosis imply
More clusters
33
What does a negative kurtosis imply?
Less clusters
34
What data would be considered discrete?
Nominal
| Ordinal
35
What data would be considered continuous?
Interval
36
What test tell us if interval data is normally distributed/ of equal variances between the groups?
Levene’s test
37
What do we do when data is NOT normally-distributed?
1. Use statistical test that doesn’t require parametric test (non parametric tests)
2. Transform data to a standardized value ( z-score or log)
38
What do we always run, even if the data isn’t normally distributed?
Descriptive statistics & graphs
39
What error is it when the researcher rejects the null hypothesis when it is actually TRUE?
Type 1 error ( alpha error)
40
What error is it when the researcher accepts the null hypothesis when it is actually FALSE?
Type 2 error ( beta error)
41
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?
Power
42
T or F
| The smaller the difference between groups necessary to be considered “significant”, the greater sample size needed.
True
43
What are the three sample size determiners?
1. Minimum difference between groups deemed significant
2. Expected variation of measurment
3. Type 1 & 2 error rates & confidence intervals
44
What are the steps to getting a p value?
1. Critical value calculated
2. Compared to appropriate table of probabilities
3. Probability value is obtained
45
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
True
46
T/ F
P value is picked after the study is run
False
47
When is p value statistically significant?
When it is lower than the picked value (5%)
48
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?
Reject the null
49
What are 4 interpretations of a pre-set (a priori) p value?
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
What are the 3 required assumptions of interval/ratio data?
1. Normally distributed
2. Equal variances
3. Randomly-derived & independent
51
What are the most common selections for a confidence interval?
90%
95%
99%
52
What are the two things that confidence intervals are based on?
1. Variation in sample
| 2. Sample size
53
T/F
| If we hope over 1.0 in the confidence interval ( go from neg to pos) then it is statistically significant
False ( if it crosses over 1.0, it ISN’T statistically significant)
54
What does a 95% confidence interval mean?
We are 95% confident that the “true” difference or relationship between the groups is contained within the confidence interval range
55
T/F
| Statistical significance doesn’t confer meaningful clinical significance
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
What is the first key question when determining the correct statistical test?
What data level is being recorded?
- order/ magnitude
- equal, consistent distances
57
What is the second question to ask to correctly select a statistical test?
2. What type of comparison/assessment is desired?
- correlation
- event/occurrence/ time to event
- outcome prediction/ association (OR)
- frequencies/counts/proportions
58
What is the third question to ask to correctly select a statistical test?
3. How many groups are being compared
| - 2 0r 3
59
What is the 4th question to ask to select the correct statistical test?
4. Is the data independent or related?
60
This test provides a quantitative measure of the strength (magnitude) & direction of a relationship between variables
Correlation
61
What is the nominal correlation test?
Contingency coefficient
62
What is the ordinal correlation test?
Spearman correlation
63
What is the interval correlation test?
Pearson correlation
64
Greater than 5% for a Pearson correlation just means there is no linear correlation; what may still be present though?
Non-linear correlation
65
This correlation test controls for confoundings
Partial correlation
66
What happens when a p value is greater than 5%?
It’s not linear
67
What is the time to event/ event occurrence test ?
Survival test
68
This test compares the proportion of events over time, or time to events, between groups
Survival test
69
What is a nominal survival test?
Log-rank test
70
What is the ordinal survival test?
Cox-proportional hazards test
71
What is the interval survival test?
Kaplan-Meier test
72
How can we represent all survival tests graphically?
By a Kaplan Meier curve
73
What is the outcome PREDICTION/ association test?
Regression
74
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
Regression
75
What is the nominal regression test?
Logistic regression
76
What is the ordinal regression test?
Multinomial logistic regression
77
What is the interval regression test?
Linear regression
78
For nominal data of greater than 5 cell counts and 2 or more groups, what test should we use?
Chi square
79
For nominal data of less than 5 cell counts and 2 or 3 groups what test should we use?
Fisher’s exact test
80
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
True
81
What subsequent tests should be run on a nominal data that 3 or more comparisons are found to be statistically significant?
Bonferroni test of inequality
| Bonferroni correction
82
This test adjusts the p value for number of comparisons being made. It is very conservative
Bonferroni test of inequality
83
When using nominal related data in 2 groups, what test should we run?
McNemar test
84
When using nominal related data in 3 or more groups, what test should we use?
Cochran
85
When using ordinal independent data in 2 groups, what test should we run?
Mann-Whitney test
86
When using ordinal independent data in 3 or more groups, what test should we use?
Kurskal-Wallis test
87
When running a Kruskal Wallis test, when 3+ group comparisons are significant then we must perform a ______________ to determine where differences are.
Post-hoc test
88
When using ordinal paired data of 2 groups, what test do we run?
Wilcoxon signed rank test
89
When using ordinal paired data with 3 or more groups, what test should we run?
Friedman test
90
What are 3 post hoc tests for 3 or more group comparisons in ordinal data?
Student Newman Keul Test
Dunnett test
Dunn test
91
Which post hoc test compares all to a single control
Dunnett test
92
What post hoc test compares all possible comparisons and the groups must be equal in size?
Student Newman Keul test
93
What post hoc test compares all comparisons possible but the groups are not of equal size?
Dunn test
94
When using independent interval data from 2 groups, what test should we run?
Student t-test
95
When using independent interval data from 3 or more groups, what tests should we run?
ANOVA
| MANOVA
96
T/F
| ANOVA test compares the means of all groups against a single DV
True
97
T/F
| MANOVA test compares the means of all groups against multiple DVs?
True
98
When using related interval data from 2 groups, what test should we run?
Paired t test
99
When using related interval data from 3 or more groups, what tests should we run?
ANOVA
| MANOVA
100
T/F
| Turkey test is a post hoc test for interval dat that is slightly more conservative then the Stu.N.K test.
True
101
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.
True
102
This correlation test shows relationship or agreement between evaluators (consistency of decisions, determinations)
Kappa statistics
103
what does a kappa test of +1 mean?
The observers perfectly classify everyone exactly the same way
104
What does a kappa test of 0 mean?
There is no relationship at all between the observers classifications, above the agreement that would be expected by chance
