Flashcards in CHAPTER: Stats//Behavioral Deck (36):

1

## Type of study that measures odds ratio - whats the equation

###
Case control

Retrospective (why can't calc RR)

Exp grp = cases = diseased

Control = disease FREE

OR = ad / cb

2

## Type of study that measures relative risk - equation

###
Cohort study

Prospective or historical

RR = (a/a+b) / (c/c+d)

Evaluation of the people who got the disease in some way (what put these people at higher risk?!)

3

## Name phase 1-4 of a clinical trial

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1 = is it safe = healthy vol

2 = does it work = small grp pts w/ disease

3 = is it as good or better = randomly assigned to treatment v placebo

4 = cant it stay = post-marketing surveillance for long term adverse SE

4

## What is an ecological survey?

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Study of POPULATIONS

How frequently does x pair with y outcome in pop data

5

## What is a cross over study

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Rd 1 = a placebo and trt grp

Washout

Rd 2 = grps get the other treatment

Pro = pts serve as own controls

6

## In a 2x2 table, what is the x vs y axis

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X = disease +/-

Y = test, RF or intervention +/-

7

## Equation for incidence + prevalence - which value is affected by disease recurrance

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Incidence = # new cases/#people @ risk

Prev = #existing cases / total # ppl

Only prevalence is affected by recurrence (add some back into existing case pool)

Similarly, cures + death only remove from existing cases

If a drug ↑survival but does not cure: ↑prev, no change incidence

8

## What is AR + equation

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Proportion of disease occurrences attributable to the exposure

AR = (a/a+b) - (c/c+d)

AR is subtraction, RR is division

9

## Equation relative risk reduction

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*Proportion of risk reduction* due to intervention

RRR = 1-RR

10

## Absolute risk reduction equation

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*Difference in risk* due to intervention

ARR = event rate (control) - ER (trt)

ARR = (c/c+d) - (a/a+b)

ER is one of those two variables, don't separate a+b values

Switch the AR equation

11

## Define + equation NNT

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NNT for 1 pt to BENEFIT

NNT = 1/ARR

12

## Define + equation for NNH

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# pts need to be exposed to a RF for 1 pt to be harmed

NNH = 1/AR

13

##
Another word for precision is...

How does precision change with random error, SD

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Precision = reliability (how close 3 hits are)

↑Random error ↓precision

↑precision - ↓SD (duh)

14

## Another word for accuracy is... what type or error changes accuracy?

###
Accuracy = validity (are you on the target)

Does this test measure what it should

Systemic error ↓accuracy

15

## What is procedure bias? How reduce it

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Different grps not treated the same

Ex: trt grp spent more time in a specialized hospital

BLIND + PLACEBO

16

## What is the Pygmalion and Hawthorne effects? How reduce

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Pygmalion = researcher's belief changes outcome (self fulfilling prophecy)

Hawthorne = subject behavior changes as they know they are being studied (ex: doctors in a quality control study)

Blinding + placebo

17

## Best way to control confounding

### Matching

18

## What type of bias should you keep in mind for screening tests

### Lead time bias - did this screening test actually extend someone's life or just detect the disease earlier

19

## What is the mean, med, mode in normal dist vs positive skew vs negative skew

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Normal dist: mean = med = mode

+ skew = hump to L, long tail to the R

mOde E > O

20

## What is a type 1 error? Alpha?

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T1 error = false positive

You said there was an effect but none exists

Alpha = probability making T1 error

21

## Why do you compare alpha to the p value?

### If p

22

## What is a type 2 error? Beta?

###
False neg

You said my data is cramp, but it really isn't! There is an effect

B = probability making T2 error

23

## What is power? 3 ways to ↑power?

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Power = 1-B

Ability to detect a difference when one really exists (you're subtracting the likelihood that you don't ID a relationship)

↑power if you ↓B

1. ↑SS (pwoer in #s)

2. ↑expected effect size

3. ↑precision of your tests

24

## If CI = mean +/- Z(stand error of mean), what is Z for a 95 vs 99% CI?

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95% CI, Z = 1.96

99% CI, Z = 2.58

25

## If you are given a MEAN and the 95% CI is (-1, 1), is the value stat sig?

###
NO

Mean 0 has to be out of the CI

You're average can't be 0!

26

## If you are given OR or RR and the 95% CI is (0-2), is the value stat sig?

###
NO

You're base like risk or odds are 1 - can't be in the CI

27

## If you are given 2 groups, and the CI intervals overlap, is there a sig difference between them?

### No - cannot overlap

28

## What equation tells you the P of at least 1 + sample test result?

###
1 - P (all events being the same)

1 - P (all 8 tests are neg)^8

29

## Stat test for means of 2 grps

### T or z test

30

## Stat test for means of 3+ grps

### ANalysis Of VAriance

31

## Stat test for 2+ % or proportions of *categorical* outcomes

###
Chi^2

Chi-tegorical

32

## Stat test to det linear relationship between 1 dep variable and 2+ indep variables

### Multiple linear regression

33

## What is the name of the correlation coefficient

###
r

Varies between -1 -> 0 -> 1

Positive vs negative tells you direction of the line

Closeness of data to that lines tells you 1 vs 0

34

## MediCARE vs medicAID

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Care for old, disabled, ESRD

Aid the poor

35

## Name medicare pts A-D

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A = hospital insurance

B = basic medical billing = doc fees, dx tests

C = A+B, delivered by approved private companies

D = prescription drugs

36