Biostats

Question 1

Null Hypothesis (Ho)

Answer 1

-research perspective that states there will be no (true) diff b/w the groups being compared!!!

Question 2

statistical perspectives

Answer 2

• superiority
• non-inferiority
• equivalency

Question 3

mode, median, mean, outliers

Answer 3

• mode- most freq/common
• median- middle
• mean- avg
• outliers- impact the MEAN!!

Question 4

inter-quartile range (IQR)

Answer 4

-middle 50%

Question 5

Shapes of data distribution- symmetrical

Answer 5

(bell-shaped)

-normally distributed!!!

Question 6

std deviations

Answer 6

• 1 std deviation above/below mean- 68% of pop
• 2- 95%
• 3- 99.7%

Question 7

Positively Skewed

Answer 7

• tail points to the right

- mean > median

Question 8

Negatively skewed

Answer 8

• tail points to left

- mean < median

Question 9

Skewness- measures?

Answer 9

• measure of the asymmetry of distribution

- a perfectly-normal distribution is symmetric and has a skewness value of 0

Question 10

3 primary levels for data

Answer 10

• nominal
• ordinal
• interval

Question 11

2 key attributes of data measurement

Answer 11

• Magnitude

- fixed interval

Question 12

Nominal

Answer 12

• dichotomous/binary (2 categories); non-ranked named categories
• NO magnitude, NO interval

Question 13

Ordinal

Answer 13

• ranked categories

- YES magnitude, NO interval

Question 14

Interval

Answer 14

• units!!

- YES magnitude, YES interval

Question 15

required assumptions of interval data

Answer 15

• normally distributed
• equal variances
• LEVENE’S TEST- when want to know if variances or spread of groups are equal!!

Question 16

Handling interval data not normally distributed

Answer 16

-cant be interval!

Question 17

4 key questions to select the correct statistical test

Answer 17

• Data level- magnitude, interval
• type of comparison
• how many groups- 2 or 3 or more
• data independent or related (paired)

Question 18

type of comparisons

Answer 18

• correlation
• regression (prediction)
• survival comparison (time)
• group comparison

Question 19

Correlation (r)

Answer 19

• quantitative measure of strength and direction of a relationship b/w variables
• values range from -1.0 to +1.0
• +1.0- perfectly positive- 45 degree angle, positive slope
• 0.0- no association
• -1.0- perfectly negative- 45 degree angle, neg slope

Question 20

Correlation tests

Answer 20

• nominal- contingency coefficient
• ordinal- spearman correlation
• interval- pearson correlation

Question 21

Survival tests- represented by?

Answer 21

(TIME)

-kaplan-meier curve

Question 22

Survival tests

Answer 22

• nominal- Log-rank test
• ordinal- cox-proportional hazards test
• interval- kaplan-meier

Question 23

Regression tests

Answer 23

(prediction)

• nominal- Logistic regression
• ordinal- multinomial logistic regression
• interval- linear regression

Question 24

Nominal data- 2 groups of indep data; 3 or more groups of indep data; 2 or more groups w expected cell count of <5

Answer 24

• (Pearson’s) Chi-square test- 2 groups of indep data
• Chi-square test of independence- 3 or more groups of indep data
• Fisher’s Exact test- 2 or more groups w expected cell count of <5

Question 25

Nominal data- 3 or more groups of indep and related data- post-hoc testing

Answer 25

-Bonferroni test of inequality

Question 26

Nominal data- 2 groups of paired/related data, 3 or more groups of paired/related data

Answer 26

- McNemar test- 2 groups | - Cochran- 3 or more groups- Bonferroni test of inequality

Question 27

Ordinal data- 2 groups of indep data, 3 or more groups of indep data

Answer 27

- Mann-Whitney test- 2 groups | - Kruskal-Wallis test- 3 or more

Question 28

Ordinal data- 2 groups of paired/related data, 3 or more groups of paired/related data

Answer 28

- Wilcoxon Signed Rank test- 2 | - Friedman test- 3 or more

Question 29

Ordinal data- 3 or more groups of indep or related data- post-hoc test

Answer 29

- Student-Newman-Keul - Dunnett - Dunn

Question 30

Interval data- 2 groups, 3 or more groups of indep data, 3 or more groups w Cofounders

Answer 30

- student t-test- 2 - ANOVA (analysis of variance)(1 DV), MANOVA (mult analysis of variance)(2 or more DVs)- 3 or more - ANCOVA, MANCOVA- w cofounders

Question 31

Interval data- 2 groups, 3 or more groups of PAIRED data, 3 or more groups w Cofounders

Answer 31

- paired t-test- 2 - repeated measures ANOVA, repeated measures MANOVA- 3 or more - ANCOVA, MANCOVA- w cofounders

Question 32

Interval data- post-hoc tests for 3 or more

Answer 32

- student-newman-keul test - dunnett test - dunn test - turkey or scheffe tests - bonferroni connection

Question 33

Kappa statistic

Answer 33

- correlation test showing relationship or agreement b/w evaluators (consistency of decisions) - +1- observers perfectly classify everyone exactly the same way - 0- no relationship at all b/w the observers' classifications - +1- observers classify everyone exactly the opp of each other

Question 34

type 1 error

Answer 34

-rejecting Null hypothesis when it is actually TRUE, and you should have accepted it!! (claim a diff when there isnt 1)

Question 35

type 2 error

Answer 35

-not rejecting null hypothesis when it is actually FALSE, and you should have rejected it (when there is a diff)

Question 36

Power (1-B error)

Answer 36

- ability of a study design to detect a true difference if 1 truly exists - sample size- inc power!!!

Question 37

p value

Answer 37

- probability of making type 1 error~ - <5%- can reject the null hypothesis- statistically significant - >5%- not statistically significant

Question 38

Confidence Interval (CI)

Answer 38

- 95% confident that the true diff or relationship b.w the groups is contained within the confidence interval range - if CI crosses 1.0- NOT significant (p>0.05)