Exam 1

Question 1

Efficacy

Answer 1

How beneficial a specific intervention, procedure, regimen, or service is under ideal conditions (lab)

Question 2

Effectiveness

Answer 2

How beneficial a specific intervention, procedure, regimen, or service is when deployed in the field in routine circumstances (real world)

Question 3

Heirarchy of evidence quality

Answer 3

1. Systematic reviews and meta-analysis
2. Clinical trial in humans (all criteria met)
3. Longitudinal cohort studies
4. Case-control studies
5. Human trial without concurrent controls
6. Descriptive and cross-sectional studies
7. Case reports & case series
8. Personal opinion, subjective impressions, anecdotal accounts

Question 4

Criteria for clinical trial in humans

Answer 4

• Sufficient & appropriate subjects
• Subjects randomly allocated
• Use placebo in double-blind
• Tested agent is closely assessed
• Reliability of measurements (calibrate machines)
• Sufficient duration
• Minimal loss to follow-up (Has to be random loss)
• Specific endpoints have to be clearly defined in advance
• Statistical analysis is appropriate

Question 5

Prospective study

Answer 5

Before disease occurs in subjects

Question 6

Retrospective study

Answer 6

After disease has occurred in subjects

Question 7

Cohort study

Answer 7

Separate subjects based on exposure, then find the prevalence of disease in each group

Question 8

Case-Control study

Answer 8

Separate subjects based on whether they have a disease or not, then find exposures of each group

Question 9

Cross-sectional survey

Answer 9

Disease and exposure assessed at the same time in a very large population (Snapshot)
Not always possible to distinguish whether exposure preceded or followed disease

Question 10

Case report

Answer 10

Describes experience of a single patient or groups of patients with similar diagnosis

May lead to formulation of a hypothesis

Question 11

Case series

Answer 11

A collection of individual case reports

Investigating activities of infected individual leads to hypothesis which is tested by comparing those with and w/o disease in a later case-control study

Question 12

Nominal variables

Answer 12

A scale based on categories

Ex: gender, political party, marital status

Question 13

Ordinal variables

Answer 13

A scale based on classification of an observation according to its relationship to other observations
Ex: Poor-fair-good rating scale

Question 14

Crossover study

Answer 14

A longitudinal study in which subjects receive a sequence of different treatments (or exposures).

Question 15

Interval variables

Answer 15

A scale based on equal units of measurement; distance between any 2 numbers is of known size
Zero point is arbitrary
Ex: Fahrenheit and centigrade temperature scales

Question 16

Ratio variables

Answer 16

A scale based on equal units of measurement and a true zero point at its origin
Ex: Mass, time

Question 17

Population vs Sample

Answer 17

Population = Whole group of people (mean=µ, SD-σ)
Sample = Part of the population (mean=x̅, SD=S or SD)

Question 18

Mode

Answer 18

Most frequent measurement

Most useful with nominal scale, but may be used with any

Question 19

Median

Answer 19

Measurement right in the middle when put in order

Most useful with ordinal, but may be used with higher order scales
Insensitive to extreme values

Question 20

Mean

Answer 20

Arithmetical average: sum of measurements divided by total # of measurements

Most useful with interval or ratio measurement scales

Question 21

Range

Answer 21

Difference between largest and smallest measurements

Question 22

Interquartile range

Answer 22

X25th percentile - X75th percentile

Question 23

Variance (s^2, MS)

Answer 23

Unbiased estimate of population variance

Sum of squares/total # in sample
Subtract 1 (degrees of freedom)

Question 24

Sum of squares

Answer 24

Subtracting sample mean from each of the measurements, squaring the result to eliminate negative #s, then add all of these

Question 25

Degrees of freedom (df)

Answer 25

``` N - 1 (N = # of variables) # of independent observations (# of observations that are "free to vary") ```

Question 26

Standard deviation (SD)

Answer 26

Positive square root of variance

Question 27

Coefficient of variation (CV)

Answer 27

100 x SD/Mean The comparison of the size of the standard deviation to that of the mean

Question 28

Standard error of the mean (SE or SEM)

Answer 28

Measurement of how good we think mean is SD/Square root of sample size (N) Bigger sample size = lower standard error

Question 29

Difference between SD and SE

Answer 29

SD is used to measure variability of individual subjects/entities around a sample mean (variability of individual measurements from the mean) SE is used to assess how accurately a sample mean represents a population mean (variability of the mean if you repeated the experiment many times)

Question 30

Bar charts

Answer 30

``` Categorical data (Nominal, ordinal) Labels under each bar ```

Question 31

Histograms

Answer 31

Bar charts for continuous data | Axis labels not necessarily centered under bars

Question 32

Box-whiskers plots

Answer 32

Box represents middle 50% of data Line represents median Whiskers extend to remaining data (circles/asterisks represent outliers)

Question 33

Dot plots

Answer 33

Continuous data in groups | Shows relative location & spread of each group

Question 34

Funnel effect

Answer 34

Only see half the data in journals because funders will not publish negative findings that go against their products

Question 35

Impact factor

Answer 35

Total # citations to articles in journal / Total # of articles published

Question 36

Types of papers published in journals

Answer 36

(1) Research reports (2) Reviews of the literature to summarize knowledge in a particular area (3) Commentaries

Question 37

Difference between statistical and clinical significance

Answer 37

1% change in plaque index is statistically significant but not clinically significant at all

Question 38

Prevalence of a disease

Answer 38

How many people had it at a specific point in time

Question 39

Booleans

Answer 39

AND - searches for another word in addition (narrows) NOT - doesn't include a certain word (narrows) OR - search 2 words separately (broadens) "" - search exact phrase (narrows)

Question 40

PICO

Answer 40

P- Patient problem I- Intervention, prognostic factor or exposure C- Comparison O- Outcome

Question 41

Types of hypotheses

Answer 41

Research - What we are trying to prove; prediction Null - a mathematical statement of no difference Alternate - covers all that the null doesn't

Question 42

Directional (one-tailed) hypothesis

Answer 42

Trying to prove one scenario (guys smarter than girls)

Question 43

Non-directional (two-tailed) hypothesis

Answer 43

Allowing either outcome to be possible (guys or girls could be smarter) *This is what we will use in class*

Question 44

Dependent variable

Answer 44

• The variable we measure and compare (intelligence) • Sometimes called the outcome variable or response variable

Question 45

Independent variable

Answer 45

• The variable we manipulate or the “grouping variable” (gender) • Sometimes called a predictor variable

Question 46

Type I Error (α or p-value)

Answer 46

Probability of rejecting null hypothesis when it is true

Question 47

Type II Error (ß)

Answer 47

Probability of accepting null hypothesis when it is false

Question 48

Methods to increase power

Answer 48

- Increase type I error willing to tolerate (ß + power = 1) - Increase sample size - Increase deviation from null hypothesis willing to tolerate - Decrease variability - Use a directional alternate hypothesis if appropriate - Use most efficient/powerful statistical test

Question 49

Reject H0 if and only if

Answer 49

p ≤ α

Question 50

Central limit theorem

Answer 50

In random samples of N observations drawn from a population, the sample means will be approximately normally distributed

Question 51

Z score

Answer 51

z = x̅i - µ ---------------- σ / SqRt(N)

Question 52

Z score distances

Answer 52

``` 68% = within 1 SD of mean 95% = within 2 SD of mean 99% = within 3 SD of mean ```

Question 53

t-distribution

Answer 53

Used when sample size is small (<30) Calculation is exact same as z score Has smaller mound & thicker tails

Question 54

Confidence interval for a mean

Answer 54

Consists of lower confidence bound & upper confidence bound with the population mean contained in the interval (1-α)% of the time