Behaviorial Science/Biostats Flashcards Preview

USMLE Step 1 Random Facts > Behaviorial Science/Biostats > Flashcards

Flashcards in Behaviorial Science/Biostats Deck (36):
1

power of a study increases w/

increased sample size, expected effect size, precision management

2

power =

1 - beta
beta = stating there ISN'T an effect/difference when ONE EXISTS

3

sensitivity =

test detects dz when dz present; screening test (rule out a dz)

1 - FN rate
TP/(TP + FN) aka TP/total dz +
a/(a+c)

4

specificity =

test indicates NO DZ when dz actually absent; confirmatory test (rule in a dz)

1 - FP rate
TN/(TN+FP) aka TN/total dz negatives
d/(b+d)

5

PPV

person WITH dz tested positive in test
TRUE POSITIVE!!

TP/(TP+FP)
a/(a+b)

high pretest probability = high PPV

6

NPV

person WITHOUT dz who tested negative in test
TRUE NEGATIVE!!

TN/(FN+TN)
d/(c+d)

high pretest probability = LOW NPV

7

incidence

# of new cases

8

prevalence

incidence x time

looks at ALL current cases --> tx that prolongs survival INCREASES prevalence

9

odds ratio (OR)

used in case-control studies
odds that group w/ dz exposed to risk factor divided by odds that group w/o dz exposed to risk factor = (a/c)/(b/d) =

ad/bc

10

relative risk (RR)

used in cohort studies
risk of developing dz in exposed group divided by risk in unexposed group

[a/(a+b)]/[c/(c+d)]

if low prevalence --> RR = OR

11

attributable risk

difference in risk b/w exposed/unexposed groups

Attributable Risk % = (RR - 1)/RR
[a/(a+b)] - [c/(c+d)]
event rate(of tx) - event rate(in other group)

12

Absolute risk reduction (ARR)

AR(in control) - AR(w/ tx)
[c/(c+d)] - [a/(a+b)]

13

# needed to treat

# pts needed to treat for 1 pt to benefit

1/ARR

14

# needed to harm

# of pts who need to be exposed to RF for 1 pt to be harmed

1/attributable risk

15

relative risk reduction (RRR)

[AR(control) - AR(tx)]/AR(control)

16

type 1 error (alpha)

stating there IS an effect when there ACTUALLY IS NOT (mistakenly reject null hypothesis)

b/(b+d)

17

type II error (beta)

stating there IS NOT an effect when there ACTUALLY IS (fail to reject null hypothesis)

c/(a+c)

18

95% confidence interval Z-score =

1.96

19

99% confidence interval Z-score =

2.58

20

standard error of mean (SEM) =

SD/(sq rt of n)

SD (standard deviation) = aka sigma
n = sample size

21

formula to obtain confidence limits

mean +/- [Z-score x SEM]

22

wave seen in awake stage?

beta (highest freq, lowest amp)

23

wave seen in relaxation stage?

alpha

24

wave seen in N1 stage?

theta

25

wave seen in N2 stage?

sleep spindles and K complexes

26

wave seen in N3 stage?

delta (lowest freqm highest amp)

27

wave seen in REM?

beta

28

what stage of sleep does night terrors, bedwetting, sleep walking occur

N3 - NO memory of sleep terror (as opposed to REM)

29

REM occurs due to what part of brain

PPRF (paramedian pontine reticular formation)

30

REM stage ass w/?

dreaming
loss of motor tone
erections
increased brain O2 use

31

sleep stage w/ bruxism (teeth grinding)

N2

32

sleep enuresis preferred tx

DDVAP (oral desmopressin acetate)
preferred over imipramine, indomethacin

33

key NT changes in REM sleep

increased ACh
NE reduces REM sleep

34

primary sleep stage in narcolepsy

straight to REM sleep

35

tx for narcolepsy

modafinil, amphetamines (stimulants)
sodium oxybate (GHB) - for nighttime

36

NT change in narcolepsy

decreased hypocretin-1 from lateral hypothalamus