EXAM III Material Flashcards
Define Population
All individuals
DIFFERENT from study population (the final group of individuals selected for a study)
Define Sample and state when it’s useful to be used
A subset or portion of the full population
“representatives”
Useful when studying the complete population is not feasible
Study measurements of human studies are collected based on:
Desired “variables”
Dependent variable(s) outcome variable
Independent variables
In which comparisons will be made = Statistical analysis
and inferences will be made about the sample-derived measurements and their comparisons (in relation to Null Hypothesis) & to the full population of similar subjects (generalizability)
Define Null Hypothesis
A research prospective which states that there will be no true difference b/w the groups being compared
Most conservative and commonly utilized
What statistical references can be taken by the researcher in a null hypothesis?
Superiority
Noninferiority
Equivalency
Don’t always have to show superiority; sometimes equivalency is good enough
What are the 2 key attributes of data measurement/variables in which help to determine the statistical test?
Magnitude/Dimensionality - i.e. pain level scale, satisfaction, fanciness
Consistency of scale/fixed interval - equal, measurable spacing between units - i.e. date, time, months, age groups, etc.
A 3rd one is rational/absolute zero
What are the 3 categories for data/variables based on the answers to the two key attributes of magnitude and consistency of scale?
Nominal/Dichotomous/Binary; Non-Ranked named categories
Ordinal/Ranked Categories; equal-distance
Interval/Ratio (order & magnitude & equal intervals-of-scale (units))
Define the nominal category for data/variables
Has No magnitude, No consistency of scale, No rational zero
Dichotomous, Non-ranked, Categorical
Simply labeled variables without quantitative characteristics
Descrete = Whole Numbers
No mean - cannot interpret mean
i.e. male/female, hair color, eye color, etc.
Define ordinal level of data measurement and list examples
Yes Magnitude
No Consistency of scale
No Rational Zero
Descrete = whole numbers
May calculate Mean; must be careful tho
i.e. pain level scale, ranking, satisfaction
Define Ratio/Interval level of measurement and list examples
Yes Magnitude
Yes Consistency of Scale
N/Y Rational Zero (N = Interval, Y = Ratio)
Continous = Fractional Numbers
Can calculate mean, median, standard dev.
i.e. age, number of living siblings, anything physiological measured (BP, lipid panel, etc.)
What type of data measurement is applicable while having a Parametric test (normally distributed shape of data distribution)
Interval
MMM are essentially equal
Equal dispersion of curve “tails” to both sides of MMM
What does it mean to have a positively skewed graph?
When the tail points to the right
Mean > Median
What does it mean to have a negatively skewed graph?
When the tail points to the left
Mean < Median
Define skewness, what is the value depicting a symmetric, normal distribution?
A measure of the asymmetry of a distribution
Value of 0 = perfectly normal, symmetric, equal MMM
The further from 0, the more the data is skewed
Define kurtosis and what (+) and (-) kurtosis means
A measure of the extent to which observations cluster around the mean
How well the values cluster around the mean/middle
(+) = more cluster within the graph/bell shape
(-) = less cluster within the graph/bell shape
What are the required assumptions of interval data for proper selection of a parametric test?
Normally distributed
Equal variable = Levene’s Test; used to determine if the interval data is equal; within the SBSS test
Randomly-derived and Independent
ALL must be true in order to pick Interval measurement
What question does Confidence Interval address?
What is the plausible range of possible difference or relationship within which I believe the true difference or relationship may lie?
What question does the p value address from a statistical test?
What is the single measurement value most likely to represent the true (yet unknown) difference or relationship between the groups being compared and what is the probability the difference has occurred by chance?
p value is attributed to Type I or Type II error?
Type I error = False Positive
When a test detects the presence of disease when in fact the person does not have the disease
Define p value
The probability of making a Type I error if the Null Hypothesis is rejected.
What does is mean when a graph has a kurtosis value of 0?
A perfect cluster of obversations at the mean of the bell shaped curve = a normal distribution
Which type of data(s) are discrete and why?
Nominal and Ordinal
Variables are discrete because they do not have a scale and you cannot have something in between the variables, not continuous
What is a Levene’s test and why is it used?
A test that is done when you need to determine if the data has magnitude and a balanced scale
Tells us if the data is interval data, if there are equal variances
Asses for equal variances b/w groups
What requirements must be met before choosing a Parametric test?
Interval data must be:
Normally distributed (bell-shaped curve)
Contain equal variances
Randomly-derived and independent
What type of stat test is used for non-parametric tests?
Descriptive Stats and Graphs
Data is transformed into a standardized value
(z-score or log)
These are stat tests that does not
Define Power (1-beta)
The ability of a study design/methodology/selected test statistic to detect a true difference if one truly exists b/w group-comparisons and the level of accuracy in correctly accepting/rejecting the Null Hypothesis (analogous to sensitivity in screenings)
Value is traditionally set at 20%
How does the sample size impact the power of stat significance?
The larger the sample size, the greater the likelihood/ability of detecting a difference if one truly exists
Increase in Power
Must add in anticipated drop-outs or loss to follow-ups
In determining sample sizes, would you need a larger and smaller number of samples when the differences between groups are smaller?
Need a greater number (N)
Due to the fact that there is a small difference, it will be harder to find differences in a small group, therefore you need more samples
Add in anticipated drop-outs or loss to follow-ups
What is another word for a type I error rate?
p value
If < 0.05 it is statistically significant
Determined before a study begins
Low p values allow more confidence and have a less risk of Type I error
by chance alone
Define Type I Error and state another term for it
alpha
Rejecting the Null Hypothesis when it is actually true and you should have accepted it
There is really NO TRUE DIFFERENCES b/w groups but you in error reject the null hypothesis, thereby stating that you believe there’s a difference b/w the groups when in fact, there really isn’t!
= False Positives
Define Type II Error and state another term for it
Beta
Not rejecting the Null Hypothesis when it is actually false and you should have rejected it
When there really IS A TRUE DIFFERENCE b/w the groups being compared but you in error do not reject the null and state that there is no difference when there actually is
= False Negative
What are the most common selected confidence interval values?
90%, 95%, 99%
Explain the interpretation of a 95% CI
We are 95% confident that the “true” difference (0) or relationship (1) between the groups is contained within the CI range
List the common types of measures of central tendency
Mean, Median, Mode
Outliers
Minimum and maximum range
Interquartile Range
Define the two measures of variation/spread/dispersion of data
Variance (from the mean) - the difference in each individual measurement value and the groups’ mean
Stardard Deviation - The square root of variance value
What are the 3 population percentages comprised within 1, 2, and 3 SDs around the mean of a normally distributed dataset?
1 = 68%
2 = 95%
3 = 99%
Differentiate between dependent and independent data and list the common terms used for dependent data
Dependent data is when you have data from the same/paired groups = before/after, pre/post, beginning/end, start/finish
Independent data is when you have data from different groups
What 4 questions must you ask yourself in while determining a correct stat test to use?
- What type of data is being collected/evaluated?
Nominal/Ordinal/Interval
- What type of comparison/assessment is desired?
Correlation, Survival, Regression = stop here
Frequencies, Proportions, Counts = proceed to Qs 3 and 4
- How many groups are being compared?
- Is the data independent or dependent?
What is a Correlation test, when would you want to use it, what do they tell you and whatare the types of correlation tests for the 3 data types?
Provides a quantitative measure of the strength and direction
When is a partial correlation test used?
When you are performing a correlation test and want to control for confounding variables
What is a contingency coefficient test and what type of data is it used for?
A correlational test that determines the strength and relationship between variables
Nominal Data
What type of test is a Spearman/Kendall Correlation test and what type of data is it useful for?
A Correlational test used to provide a quantitative measure of the strength and direction of a relationship between variables
Ordinal Data
What type of test is a Pearson Correlation test and what type of data is it useful for? What happens when you have a p-value > 0.05?
A type of stat test that measures the correlation quantitatively of strength and direction of a relationship between groups
Interval Data
If there is a sig. p value, you can say that there is a linear correlation
What are survival tests, what are they used for, how can the data be represented as and what are the tests for each of the 3 data types?
Used to measure an event occurrence/proportion of events/time-to-an event
All can be represented as a Kaplan-Meier Curve
Nominal = Log Rank Test
Ordinal = Cox Proportional Hazard Test
Interval = Kaplan-Meier Test
What type of test is a log-ranked test and what type of data is it used for?
A type of survival test that compares the occurrence/proportion of events/time-to-an event between groups
Nominal Data
What type of test is a Cox-Proportional Hazard Test and what type of data is it used for?
A type of Survival test used to compare a proportion of events/occurrence/time-to-an event between groups
Ordinal Data
Able to represent data on a Kaplan-Meier Curve
What type of stat test is the Kaplan-Meier Test and what type of data is it used for?
A type of survival test used to compare a proportion of event/occurrence/time-to-an-event between groups
Interval Data
What is a regression test and what are the 3 types of test under each data category?
Tests done to measure the relationship/association between variables by making a prediction about the dependent variable outcome by going back to old data
Able to calculate OR
Nominal = Logistic Regression
Ordinal = Multinominal Logistic Regression
Interval = Linear Regression
What type of data is used for a logistic regression test?
A regression test that allows you to test the relationships/associations by going back to old data and making a prediction about the dependent variable outcome
Nominal Data
What type of data is a Multinominal Regression Test used for?
A type of regression test used to measure the relationship/association of groups by going back to old data and making a prediction of the dependent variable/outcome
Ordinal Data
What type of data is used for a Linear Regression Test?
A type of regression test that measures the relationship/association of groups by going back to old data and making a prediction of the dependent variable/outcome
Interval Data
What type of tests are used for nominal data when you have 2 groups? (for dependent and independent data)
(before/after, pre/post, start/finish)
Dependent/Paired data = McNemar Test
Independent data = Pearson’s Chi-Squared and Fisher’s Exact (able to handle small numbers)
What type of tests are used for nominal data when you have 3 or more groups? (for dependent and independent data)
Independent Data = Chi-square and Fisher’s Exact
Dependent/Paired Data = Cochran
All are under the category of Bonferroni Test of Inequality - Conservative method of adjusting the p value for the # of comparisons that are being made
What is the Bonferroni test of inequality and which tests fall under that category?
Bonferroni Correction
Conservative method that adjusts the p value for the number of comparisons being made
What is a Pearson’s Chi-square test? What type of data is it used for?
A chi-squared test done when you have Nominal Data with 2 groups that contain independent data
What is a Chi-square test and what type of data is it used for? What must occur if you have a finding that is statistically significant?
A test done with Nominal data with Independent data of 3+ groups
If p-value is stat. significant, must perform a post-hoc analysis test to determine which groups are different
More likely to have a type I error if performing multiple chi-squared tests
May perform a Bonferroni test of inequality to adjust the p value for the number of comparisons that are being made
What is a Fisher’s Exact test and what type of data does it use?
Test done using nominal data with Independent data done with 3+ groups
You have an expected cell count of less than 5
This test is able to handle small numbers
What is a McNemar test and what type of data does it utilize?
Test done with nominal data when you have 2 Groups with dependent data.
dependent/paired = _(_before/after, pre/post, start/finish)
What is a Cochran Q test and what type of data does it utilize? What is its relation with the chi-squared test?
Test done with nominal data with dependent/related data done on 3+ groups
If there is a p-value that is stat. significant, must perform a post-hoc analysis to determine which group is different
May use a Bonferroni test of inequality/Bonferroni correction; a conservative approach that adjusts the p-value for the number of comparisons that are being made
What are the 2 tests that are performed with independent variables that contain ordinal data?
Mann-Whitney test
Kruskal-Wallis test - post-hoc test if sig. p value is found
Both are used for interval data that does not meet the parametric requirements
Both compare the median value between groups
What are the 2 tests that are used when you have dependent/paired variables with ordinal data?
Wilcoxon Signed Rank test
Friedman test - If p-value is sig. must perform a post-hoc test to see which group is different
Both tests compare the median between groups
Both tests are used with interval data that does not meet parametric requirements
What tests are used when you have 2 groups with ordinal data? (independent and paired data)
Independent data = Mann-Whitney test (3+ groups, p-value sig. = post-hoc test to find where difference lies)
Dependent/Related data = Wilcoxon Signed Rank (pre/post, before/after, start/finish)
Both tests compare the median values
Both tests used for interval data that does not meet parametric requirements
What type of tests are used when you have ordinal data with 3 or more groups? (independent and related data)
Independent = Kruskal-Wallis
Dependent = Friedman
Both tests compare the median values
Both tests must perform a post-hoc test if you find a sig. p-value
Used for interval data that does not meet parametric requirements
What are the characteristics of stat tests that require a post-hoc test?
When the test has 3 or more groups and you have a statistically significant p-value
What post-hoc tests are used when you have nominal and ordinal data with 3 or more groups? (3)
Student-Newman-Keul Test - compares all pairwise comparisons possible; groups must be equal in size
Dunnett Test - compares all pairwise comparisons possible against a single control; groups must be equal in size
Dunn Test - compares all pairwise comparisons possible; groups do not have to be equal
What is a Dunn test and when is it useful?
A post-hoc test used when you have ordinal data with 3 or more groups (independent OR paired/related)
Compares all pairwise comparisons possible
Groups do not have to be equal in size; as opposed to Dunnett and Student-Newman-Keul test
What is a Student-Newman-Keul test and what is it useful for?
A post-hoc test done when you have a significant p-value with ordinal data with 3 or more groups and you need to determine where the difference lies.
Compares all pairwise comparisons possible and groups must be equal in size; as opposed to the Dunn Test
What is a Dunnett test and what is it useful for?
A post-hoc test done when you have a significant p-value and must find where the difference lies when you have 3 or more groups with ordinal data.
Compares all pairwise comparisons against a single control and all groups must be equal in size
What are the possible tests when you have interval data with independent variables? (5)
Analysis of Variance (ANOVA) - 3+ groups
Analysis of Co-Variance (ANCOVA) - 3+ groups
Multiple Analysis of Variance (MANOVA) - 3+ groups
Multpile Analysis of Co-Variance (MANCOVA) - 3+ groups
Student T-test - 2 groups
What is a Student T-test? When is it useful?
Test performed when you have interval data with 2 groups with independent data
Compares the means of all groups, along with intra- and inter-group variations against a single dependent variable
What is a Analysis of Variance (ANOVA) test and what is it useful for?
Test used when you have interval data when you have 3 or more groups with independent variables
Compares the means of all groups along with the inter- and intra- group variations against a single dependent variable
Able to use with 2 groups as well
What is a Multiple Analysis of Variance (MANOVA) and what is it useful for?
Test done when you have interval data with 3 or more groups that have independent data against multiple dependent variables
Compares the means of all groups and the inter- and intra- group comparisons
Must use a post-hoc test if p-value is stat. sig.
What is an Analysis of Co-Variance (ANCOVA) and what is it useful for?
A test done when you have interval data with 3 or more groups containing independent variables
Compares the means of all groups along with inter- and intra- group variations against a single dependent variable while controlling for the co-variance of confounders
What is a Multiple Analysis of Co-Variance (MANCOVA) test and what is it useful for?
Test used when you have interval data with 3 or more groups with independent variables
Compares the means of groups along with inter- and intra- group comparisons against multiple dependent variables while controlling for the co-variance of confounders
What tests are useful when you have interval data with 2 groups? (independent and dependent/related)
Independent = ANOVA, MANOVA, Student t-test
Dependent/Related = Repeated Measures ANOVA, Repeated Measures MANOVA, or Paired t-test
What tests are useful when you have interval data with 3 or more groups? (independent and dependent variables)
Independent = ANOVA or MANOVA
Dependent/Related = Repeated measures of ANOVA or Repeated measures of MANOVA
What are the 3 tests that are useful when you have interval data with dependent/related variables?
Repeated Measures ANOVA
Repeated Measures MANOVA
Paired t-test
What is a paired t-test and what is it useful for?
A test done when you have interval data with 3 or more groups with dependent/related data
Compares the mean values between groups that are related
What is a Repeated Measure ANOVA and what is it useful for?
Repeated Measure Analysis of Variance
Useful when you have interval data with 3 or more groups containing dependent/related/paired data
Compares the means of all groups along with inter- and intra-group variations of related data against a single dependent variable
Able to control for confounders
If confounder is present = Repeated Measures ANCOVA or Repeated Measures MANCOVA —> if sig. p-value = Bonferroni test or Scheffe or Dunn or Student-Newman-Keul or Dunnett test
What is a repeated measure MANOVA test and what is it useful for?
Repeated Measure Multiple Analysis of Variance
Useful when you have interval data with 3 or more groups with dependent/paired/related variables
Compares the means of all groups along with inter- and intra- group variations of related data against multiple dependent variables
Able to control for confounders; however if a confounder is present, must perform a post-hoc test; Repeated Measures ANCOVA or Repeated Measures MANCOVA
If p-value is sig. = Bonferroni test/Tukey/Scheffe/Dunn/Student-Newman-Keul/Dunnett tests
What are the post-hoc tests that are performed when you have interval data with 3 or more groups comparisons?
Tukey/Scheffe Test
Bonferroni Test
Dunn/Dunnett Test
Student-Newman-Keul Test
What is a Tukey/Scheffe Test? What is it useful for?
A post hoc test performed when you have 3 or more groups with interval data
Compares all pairwise comparisons possible
All groups must be equal in size
Tukey - slightly more conservative than Student-Newman-Keul Test
Scheffe - is less affected by violations in normality and homogeneity of variances
What is a kappa statistic?
An agreement that is made between evaluators (apart of the validation/assessment committee); consistency of “decisions”, “determinations”
+1 = observers classify everyone the same way
0 = no relationship at all between the observers classifications above the agreement that would be expected by chance
-1 = observers classify everyone exactly opposite of each other
(+) = good agreement
(-) = poor agreement
What is a kappa interpretation and what are the values that are associated with it?
Used with a kappa statistic which is an agreement between evaluators
+1 = observers classify everyone the same way
0 = no relationship at all between the observers classifications above the agreement that would be expected by chance
-1 = observers classify everyone exactly opposite of each other
(+) = good agreement
(-) = poor agreement
What checklists are used for Interventional studies? (2)
Consort Checklist - CONsolidated Standards Of Reporting Trials
PRISMA Checklist - Preferred Reporting Items for Systemiatic reviews and Meta-Analyses
What type of study is the consort checklist used for? What type of trials is it used for?
Consort - randomized (clinical) trials = interventional studies
CONsolidated Standards Of Reporting Trials
Extension Documents - design extensions for non-inferiority and equivalence trials
Cluster and Pragmatic Trials - broadly defined as randomized, controlled trial whose purpose is to inform decisions about clinical practice. A philosophy as a continumm, not a dichotomy
What are the extension documents utilized for consort checklists for interventional studies?
Design extensions for non-inferiority and equivalence trials
Cluster Trials
Pragmatic Trials
What is a PRISMA checklist and what type of study is it used for?
Systematic reviews of multiple randomized trials
Preferred Reporting Items for Systematic reviews and Meta-Analyses
What type of checklist is utilized for observational studies; cohort, case-control, cross-sectional? (3)
STROBE - STrengthening the Reporting of OBservational studies in Epidemiology
STROBE-ME - Molecular Epidemiology Studies
STREGA - STrengthening the Reporting of Genetic Association studies
What type of studies are useful for the STROBE checklist?
STrengthening the Reporting of OBservational studies in Epidemiology
Useful for Observational Studies; Case-control, Cohort and Cross-sectional
What type of study is the STROBE-ME checklist useful for?
STregthening the Reporting of OBservational studies in Epidemiology-Molecular Epidemiology studies
Useful for Observational Studies; Case-control, Cohort and Cross-sectional
What type of study is the STREGA checklist useful for?
STrengthening the Reporting of Genetic Association studies
Useful for Observational Studies; Case-control, Cohort and Cross-sectional
What checklists are useful for Non-Randomized studies? (5)
GRIPS - Genetic Risk Prediction Studies
QUADAS-2 - QUality Assessment of studies of Diagnostic Accuracy in Systematic reviews
REMARK - REporting recommendations for tumor MARKer prognostic studies
STARD - STAndards for the Reporting of Diagnostic accuracy studies
TREND - Transparent Reporting of Evaluations with Non-randomized Designs (large populations)
What is a TREND checklist and what is it useful for?
Transparent Reporting of Evaluations with Non-randomized Designs
Useful for non-randomized studies
What is the REMARK checklist and what type of study is it useful for?
REporting recommendations for tumor MARKer prognostic studies
Useful for non-randomized studies
What is a GRIPS checklist and what type of study is it useful for?
Genetic Risk Prediction Studies
Useful for non-randomized studies
What is a STARD checklist and what type of study is it useful for?
STAndards for the Reporting of Diagnostic accuracy studies
Useful for non-randomized studies
What is a QUADAS-2 checklist and what type of study is it useful for?
QUality Assessment of studies of Diagnostic Accuracy in Systematic reviews
Useful for non-randomized studies
Where exactly can each checklist that is useful for all studies be located for future use?
Equator Network website
What is NCT and what is its purpose and where can it be found?
Number of Clinical Trials
A number assigned by clinicaltrials.gov once research protocol is submitted prior to study initiation
The purpose is to reduce publication bias
What type of data can be located in clinicaltrials.gov and how was it developed?
ICMJE-acceptable public registry that offers up to date data info for locating interventional studies that are starting/in progress
NIH developed site with the FDA through its national library of medicine (NLM)
