Flashcards in Lecture 24-32 - Intro To Biostats In Epidemiology Deck (38)

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1

##
What are the 3 primary levels of variable?

L24 S5

###
-nominal

-ordinal

-interval/ratio

2

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What are the 3 key attributes of variables?

L24 S5

###
-order/magnitude

-consistency of scale

-rational absolute zero

3

##
What is nominal data?

What are its characteristics?

L24 S6

###
-consists of labeled variables without quantitative characteristics

-can be dichotomous or binary in nature

-no order/magnitude

-no consistency of scale

4

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What is ordinal data?

What are its attributes?

###
-contains rank-able categories that are not evenly spaced

-yes order/magnitude

-no consistency of scale

5

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What is interval data?

What are its attributes?

L24 S8

###
-rankable categories that are evenly spaced

-arbitrary 0 value that does not mean absence of measured value

-yes order/magnitude

-yes consistency of scale

-no rational absolute zero

6

##
What is ratio data?

What are its attributes?

L24 S8

###
-rankable categories that are evenly spaced

-absolute 0 value that indicates absence of measured value

-yes order/magnitude

-yes consistency of scale

-yes rational absolute zero

7

##
What is the order of specificity of data types?

In which direction(s) can you convert data types?

L25 S12

###
Nominal < Ordinal < Interval < Ratio

Data can only be converted down in specificity, not up

8

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What percentage of data is within one, two, and three standard deviations of the mean in a normally distributed data set?

L26 S23

###
One deviation (-1 to +1):

-68%

Two deviations (-2 to +2):

-95%

Three deviations (-3 to +3):

-99.7%

9

##
What is name given to the types of tests that are used on normally distributed data sets?

L26 S23

###
-parametric test

-or-

-interval test

10

##
What determines if a data set is skewed?

What makes a data set positively skewed?

Negatively skewed?

L26 S24-25

###
-mean and median differ from one another

Positively skewed:

-mean is higher than median

-tail goes to the right/positive direction

Negatively skewed:

-mean is lower than median

-tail goes to the left/negative direction

11

##
What does skewness represent?

L26 S35

### -the measure of asymmetry of a distribution

12

##
What is kurtosis?

What do a negative, zero, and positive kurtosis represent?

L26 S37

###
-measure of the extent to which data clusters around the mean

Negative kurtosis:

-less cluster

Zero kurtosis:

-normal distribution

Positive kurtosis:

-more cluster

13

##
Calculating the mean on nominal and ordinal data can be done but it can’t be interpreted, why is this?

L26 S40-43

### The numbers assigned to data is arbitrary and can be changed. (There is no consistency of scale and there are no units)

14

##
What is the name of the test that can be used to assess for equalness of variance between groups?

L26 S44

### -Levene’s test

15

##
How do you assess data sets that are not evenly distributed?

L26 S45

###
-use tests that do not require normal distribution (non-parametric tests)

-transform the data to a standard value (z-score or log transformation) to make it normally distributed

16

##
What are type 1 and type 2 errors?

L26 S47-49

###
Type 1 error:

-when the null hypothesis is true and should have been accepted, but wasn’t

-there is no true difference between groups but it was said that there is

Type 2 error:

-when the null hypothesis is false and should have been rejected but wasn’t

-there is a true difference between groups but it was said that their isn’t

17

##
What factors should be looked at to determine if a study’s results are statistically significant?

L27 S50

###
-power: the ability of a test to detect if there are true differences between groups

-sample size: the greater the sample size the greater the studies ability to detect if there is a difference between groups

-p value

-confidence interval

19

##
What are the typical accepted type 1 and type 2 error rates?

L27 S51

###
Type 1:

-5%

Type 2:

-20%

20

##
What are some ways that p value can be interpreted as?

L27 S56

###
-probability of making a type 1 error if the null hypothesis is rejected

-probability of erroneously claiming a difference between groups when one does not really exist

-probability of obtaining group differences as great or greater if the groups were actually the same or equal

-probability of obtaining test statistic as high/higher if the groups were actually the same/equal

21

##
Where is it desired to see that there is no statistical difference between groups?

L27

###
-baseline data

-Levene’s test

22

##
What does power mean with respects to statistical significance?

L27 S50

###
-the ability of a study to determine if there is a true difference between groups

1 - (type 2 error rate)

23

##
What is a confidence interval?

L28 S63

### -percentage of confidence that statistically includes the real relationship being compared

24

##
If the confidence interval of a ratio contains the number ____________ it is statistically insignificant.

If the confidence interval of an absolute difference contains the number __________ it is statistically insignificant.

L28 S65-66

### 1; 0

25

##
What factors should be included in the interpretation of a confidence interval?

L29 S65

###
-level of confidence

-interpretation of range

-statement of statistical significance

-statement of the groups being compared

26

##
What questions should be asked when selecting a statistical test?

L29 S91

###
-what is the level of data being collected (nominal/ordinal/interval)?

-what type of comparison/assessment is desired (frequencies/counts/proportion)

-how many groups are being compared (2 or >3) ?

-is the data independent or related (from the same person or not)?

27

##
What is a correlation test?

What are the correlation tests for each data level?

L29 S75

###
-provides a quantitative measure of the strength and direction of relationship between variable

Nominal:

-contingency coefficient

Ordinal:

-Spearman correlation

Interval:

-Pearson correlation

28

##
What is a survival test?

What are the survival tests for each level of data?

L30 S81-83

###
-compares proportion of event occurrence over time between groups

-“changes over time”

-“time to event”

-can be graphed as a Kaplan-Meier curve (regardless of data level)

Nominal:

-Log-Rank test

Ordinal:

-Cox-Proportional Hazards test

Interval:

-Kaplan-Meier test

29

##
What is a regression test?

What are the regression tests for each level of data?

L30 S84-86

###
-measure of relationship between variables to predict an outcome

-able to calculate an odds ratio

-“predict”

Nominal:

-logistic regression

Ordinal:

-multinomial logistic regression

Interval:

-linear regression

30

##
What test is used to evaluate NOMINAL data of 2 INDEPENDENT groups and >3 INDEPENDENT groups?

L31 S93

###
2 groups:

-Pearson’s Chi-square test

>3 groups:

-chi-square test of independence

When there are less than 5 observations of an occurrence, Fisher’s exact test is used instead of the two listed above.

31