Kraushar

Question 1

2 X 2 tables for hypothesis testing:

(alpha, beta, and power)

Answer 1

Question 2

Cumulative Incidence Definition and Equation:

Answer 2

(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

Question 3

Null Hypothesis (Ho):

Answer 3

• states that there is no difference

Question 4

Absolute risk difference =

Answer 4

I_exposed - I_unexposed

• incidence in exposed group minus incidence in unexposed group

Question 5

Incidence equation in steady state:

Answer 5

prevalence / duration

Question 6

Relative risk =

Answer 6

I_exposed / I_unexposed

• incidence in exposed group divided by incidence in unexposed group

Question 7

Odds ratio definition and table:

Answer 7

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

Question 8

Duration equation in steady state:

Answer 8

prevalence / incidence

Question 9

Prevalence equation in steady state:

Answer 9

(incidence) X (average duration)

Question 10

2 X 2 tables for hypothesis testing:

(type 1 and 2 errors)

Answer 10

Question 11

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

Answer 11

(probability A) + (probability B)

Question 12

Type II error:

Answer 12

• 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

Question 13

power =

Answer 13

1 - beta

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

Question 14

Incidence Rate definition and equation:

Answer 14

(new cases) / (total time lapsed)

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

Question 15

Normal distribution:

Answer 15

• 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)

Question 16

2 X 2 tables for hypothesis testing:

(false hits and false misses)

Answer 16

Question 17

Type I error:

Answer 17

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

Question 18

Prevalence Definition and Equation:

Answer 18

(total cases) / (total population)

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

Question 19

Relative risk definition and table:

Answer 19

• prospective; follow
• start with the risk factor, follow them over time, see how many people get disease
  
  • everyone starts with no disease

Question 20

Probability:

Answer 20

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

A/(A+B)

Question 21

alpha =

Answer 21

• 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

Question 22

Power depends on:

Answer 22

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

Question 23

Sensitivity equation and table:

Answer 23

TP/(TP+FN)

SNOUT

Question 24

Standard deviation:

+/- 3SD contains –% of observations

Answer 24

99.7%

Question 25

beta =

Answer 25

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

Question 26

A specific test should be utilized when:

Answer 26

* false-positive can harm the patient physically, emotionally, or financially. * used to "rule-in" diagnoses when data suggest.

Question 27

Mean, median, and mode describe:

Answer 27

“central tendency”

Question 28

Aboslute risk =

Answer 28

incidence

Question 29

Standard deviation: +/- 1SD contains --% of observations

Answer 29

68%

Question 30

Bimodal distribution:

Answer 30

* 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”

Question 31

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

Answer 31

**(probability A) X (probability B)**

Question 32

Standard deviation: +/- 2SD contains --% of observations

Answer 32

95%

Question 33

A sensitive test should be chosen when:

Answer 33

* there is an important penalty for missing the diagnosis.

Question 34

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

Answer 34

overlapping dead center of the bell

Question 35

Specificity equation and table:

Answer 35

**TN/(TN+FP)** SPIN

Question 36

Mean, median, and mode regarding skew:

Answer 36

* mode insensitive (stays in bell) * median moderately sensitive * mean very sensitive (goes out to far tail)

Question 37

Right skewed distribution:

Answer 37

* 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.

Question 38

Left skewed distribution:

Answer 38

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

Question 39

Odds:

Answer 39

* a ratio of the frequency of: **A to B, or A:B or A/B**

Question 40

Absolute risk definition and table:

Answer 40

* attributable risk * a difference of relative risks * how much of getting the disease is attributable to having the risk factor

Question 41

The three main criteria for abnormality:

Answer 41

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