# Kraushar Flashcards

1
Q

2 X 2 tables for hypothesis testing:

(alpha, beta, and power)

A
2
Q

Cumulative Incidence Definition and Equation:

A

(new cases) / (total population at risk over time)

• fraction of people initially free of the outcome but who develop it over a period of time
3
Q

Null Hypothesis (Ho):

A
• states that there is no difference
4
Q

Absolute risk difference =

A

Iexposed - Iunexposed

• incidence in exposed group minus incidence in unexposed group
5
Q

A

prevalence / duration

6
Q

Relative risk =

A

Iexposed / Iunexposed

• incidence in exposed group divided by incidence in unexposed group
7
Q

Odds ratio definition and table:

A
• retrospective
• start with people who have disease, and go backwards to find risk factor
8
Q

A

prevalence / incidence

9
Q

A

(incidence) X (average duration)

10
Q

2 X 2 tables for hypothesis testing:

(type 1 and 2 errors)

A
11
Q

The probability of two mutually exclusive events, A or B, occurring =

A

(probability A) + (probability B)

12
Q

Type II error:

A
• FALSE NEGATIVE
• saying there is no difference in treatment effects when there is.
• failing to reject (accepting) the null hypothesis when it should be rejected
13
Q

power =

A

1 - beta

• power of study to pick up a difference when it actually does exist
14
Q

Incidence Rate definition and equation:

A

(new cases) / (total time lapsed)

• rate at which new disease has occurred in the population at risk per some unit time
15
Q

Normal distribution:

A
• classic bell curve
• highest density in middle, tapers off on both sides
• mean, median, and mode all in the same place (dead center of bell curve)
• dead center for all these = perfect normal distribution (Gaussian)
16
Q

2 X 2 tables for hypothesis testing:

(false hits and false misses)

A
17
Q

Type I error:

A
• FALSE POSITIVE
• saying there is a difference when there is not.
• rejecting the null hypothesis when it should be accepted
18
Q

Prevalence Definition and Equation:

A

(total cases) / (total population)

• fraction of people experiencing a condition at a given point in time.
• number cases right now
19
Q

Relative risk definition and table:

A
• prospective; follow
• everyone starts with no disease
20
Q

Probability:

A
• a proportion in which the frequency of both events are in the denominator:

A/(A+B)

21
Q

alpha =

A
• the probability you’ll make a false hit.
• Arbitrarily, p = 0.05
• false hit = type 1 error
• 5% of the time, we’ll make an error
22
Q

Power depends on:

A
• sample size (better power = more participants)
• size of effect (better power = stronger effect)
• subject compliance
23
Q

Sensitivity equation and table:

A

TP/(TP+FN)

SNOUT

24
Q

Standard deviation:

+/- 3SD contains –% of observations

A

99.7%

25
Q

beta =

A
• probability you won’t find a difference when one actually exists (false miss)
• false miss = type 2 error
• probability of missing a reality
26
Q

A specific test should be utilized when:

A
• false-positive can harm the patient physically, emotionally, or financially.
• used to “rule-in” diagnoses when data suggest.
27
Q

Mean, median, and mode describe:

A

“central tendency”

28
Q

Aboslute risk =

A

incidence

29
Q

Standard deviation:

+/- 1SD contains –% of observations

A

68%

30
Q

Bimodal distribution:

A
• think of breasts - there is a variable (like sex; M/F) under the bimodal curve
• highest density at both bells, tapers off in each direction evenly
• bimodal has two “density centers”
31
Q

The probability of two independent events, A and B, occurring together =

A

(probability A) X (probability B)

32
Q

Standard deviation:

+/- 2SD contains –% of observations

A

95%

33
Q

A sensitive test should be chosen when:

A
• there is an important penalty for missing the diagnosis.
34
Q

mean, median, and mode location in a normal distribution:

A

overlapping dead center of the bell

35
Q

Specificity equation and table:

A

TN/(TN+FP)

SPIN

36
Q

Mean, median, and mode regarding skew:

A
• mode insensitive (stays in bell)
• median moderately sensitive
• mean very sensitive (goes out to far tail)
37
Q

Right skewed distribution:

A
• tail/outliers on the right of the bell; RIGHT TAIL
• highest density on the left, tapers out toward the tail
• Mode is where the bell peaks; mean is far in the tail. Median in middle.
38
Q

Left skewed distribution:

A
• tail/outliers on the left of the bell; LEFT TAIL
• highest density on the right (where the bell is), tapers out toward the tail
39
Q

Odds:

A
• a ratio of the frequency of:

A to B, or A:B or A/B

40
Q

Absolute risk definition and table:

A
• attributable risk
• a difference of relative risks
• how much of getting the disease is attributable to having the risk factor
41
Q

The three main criteria for abnormality:

A
1. unusual
2. associated with disease
3. treatment does more harm than good