EBM Quiz 1

Question 1

Evidence Based Medicine

Answer 1

The application of population based information to decision making about individual patients

(previously clinical epidemiology)

Question 2

Case series study

Answer 2

Certain characteristics of a group (or series) of patients (or cases) are described in a published report; interesting or intriguing observations that occurred for a small number of patients, usually leads to a hypothesis and case control, cross sectional, or cohort study

Question 3

Cross sectional study

Answer 3

Do an analysis on data collected on a group of subjects at one point in time rather than over a period of time

Could be a short period of time moving to the future

Question 4

Cohort study

Answer 4

Also known as prospective studies

Moving forward in time, subjects are selected at the onset of the study and then determine whether they have the risk factor or have been exposed

(i.e. Framingham study of CV disease)

Question 5

Historical cohort study

Answer 5

A cohort study by using information collected in the past and kept in records or files (retrospective) Direction of inquiry is still forward in time, from a possible cause or risk factor to an outcome.

Question 6

Cross over study

Answer 6

A randomized trial except at a certain point in time, the subjects stop the treatment and placebo and then switch with the control group.

Unaware of which group they are in

Question 7

Double blind study

Answer 7

Subjects are randomly put into study

They do not know which group they are in

Researchers do not know which group they are in

The gold standard (double blind randomized study)

Question 8

Blind study

Answer 8

Subjects are randomly put into study

They do not know which group they are in

Question 9

Randomized clinical trial

Answer 9

The gold standard

greatest justification for concluding causality

subject to the least number of problems or biases

Patients are randomly assigned different treatments
one is treatment, the other is control
Control may be placebo or commonly used treatment

they are expensive and long

Question 10

Controlled vs uncontrolled studies

Answer 10

Can use another investigators research as control

Can use historical controls (subjects the investigator has previously treated)

Uncontrolled studies are more often used with procedures

Question 11

Primary sources

Answer 11

Published in journals
Most popular, critically acclaimed by peer reviewers before being published

Dissertations
for an academic degree, critically reviewed before a degree is given

Technical reports

Conference proceedings

Surveys

Patents

Question 12

Secondary sources

Answer 12

Review journals

Text books

Summary of research

Most newspaper articles

Question 13

Tertiary

Answer 13

Summarizes and condenses information from primary and secondary sources

Dictionaries

Encyclopedias

Almanacs

Question 14

Impact factor

Answer 14

The measure of frequency an article has been cited in the past year

Question 15

Quantitative

Answer 15

Consists of numbers that represent counts or measurements

Question 16

Qualitative

Answer 16

(Categorical)

can be separated into non numeric categories

Question 17

Nominal

Answer 17

Categories only

Data cannot be arranged in an ordering scheme
i.e. gender or occupation

Question 18

Ordinal

Answer 18

Categories are ordered, differences can’t be found or are meaningless
(i.e. health categories - poor, reasonable, good, excellent)

Question 19

Discrete random variable

Answer 19

Take on countable values

i.e. number of offspring or respirators. Or shoe size

Question 20

Continues random variables

Answer 20

The amount of time it takes to accomplish a task

(i.e. has infinite number of times to accomplish this task)

(hours-mins-secs-microsec-nanosec-etc)

Question 21

Mean

Answer 21

Average

5.4
1.1
0.42
.73
.48
1.1

add all together and divide by 6

= 1.538

Problem is one outlying variable can affect mean

Question 22

Median

Answer 22

Middle number
arrange in descending order
take middle number

if two middle numbers, add together divide by 2

Question 23

Mode

Answer 23

mode is the data set that occurs most frequently

if two values occur with the same frequency it is bimodal

if greater than two values occur with the same frequency it is multi modal

If no value is repeated there is no mode

5.4, 1.1, .42, .73, .48, 1.1 = mode is 1.1
27, 27, 27, 55, 55, 55, 88, 88, 99 = bimodal 27 & 55
1,2,3,4,5,6,7,8,9 = no mode

1,2,3,1,2,3,4,5,6,7, = multi modal 1, 2, & 3

Question 24

Weighted mean

Answer 24

values may vary in degree of importance so we use a weighted mean to adjust this

Find the mean of 3 test scores

Scores are 85, 90, 75
Weights are 20%, 30%, 50%

20+30+50
=
8150
———-
100
= 81.5 %

x̅ = ∑(w*x) / ∑w

Question 25

Standard deviation

Answer 25

the measurement of of variation of values around the mean

(how much variability from mean)

S= Square root of

           / ̅ ̅ ̅ ̅ ̅ ̅ ̅ ̅ ̅ ̅ ̅ ̅
          /   ∑ (x-x̅)² s =        / ----------- 
      √      n-1

Find the deviation of each observation from the mean, square the deviations, add them and then divide the sum by n - 1.

The square root is used to express the standard deviation on the original scale of measurement

Question 26

Variance

Answer 26

Is a measure of variation
This is equal to the square of the standard deviation
(either sample or population)

Variance examines how a set of data values vary among themselves.
Large variance means great variation within the data

Question 27

Significant and insignificant value

Answer 27

Significantly low (µ - 2σ) or Lower
Significantly high (µ + 2σ) or Higher

Values not significant: between (µ - σ) and (µ + σ)

Significance is not used unless it has been determined to be statistically significant

Question 28

Significance example

Answer 28

Mean (+) or (-) 2 times the standard deviation

Significant

If standard deviation is 1.0 and mean is 6.
2 x 1 = 2
2 (+) or (-) 6 = 4 - 8

this means
4 or lower is significant
or
8 or higher is significant

Not significant values are between 4 and 8

Question 29

σ =

Answer 29

Standard deviation in a population

Question 30

µ =

Answer 30

Mean of all values in a population

Question 31

s =

Answer 31

standard deviation in a sample

Question 32

σ² =

Answer 32

Variance

standard deviation squared

Question 33

N =

Answer 33

number of values in a population

Question 34

n =

Answer 34

number of values in a sample

Question 35

∑ =

Answer 35

The addition of a set of values

Question 36

Greek letters are used for

Answer 36

Population

Question 37

English letters are used for

Answer 37

Sample

Question 38

x =

Answer 38

Used to represent on value in a data set.

Question 39

x̅ =

Answer 39

The mean of a set of sample values