CHAPTER: Stats//Behavioral Flashcards Preview

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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

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?

Study of POPULATIONS
How frequently does x pair with y outcome in pop data

5

What is a cross over study

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

X = disease +/-
Y = test, RF or intervention +/-

7

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

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

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

*Proportion of risk reduction* due to intervention
RRR = 1-RR

10

Absolute risk reduction equation

*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

NNT for 1 pt to BENEFIT
NNT = 1/ARR

12

Define + equation for NNH

# 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

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

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

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

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?

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?

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?

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

Care for old, disabled, ESRD
Aid the poor

35

Name medicare pts A-D

A = hospital insurance
B = basic medical billing = doc fees, dx tests
C = A+B, delivered by approved private companies
D = prescription drugs

36

What type of analysis id's the cause of medical error retrospectively vs prospectively

Root cause anal = look back at ALL problems that lead to an error (fishbone)
Failure mode + effects analysis = inductive reasoning to anticipate how a process might fail