lecture 1 - introduction to evidence based medicine

Question 1

this is a statistical method that shows the relationship between two or more variables

Answer 1

regression analysis

Question 2

There is no current evidence that _____ have a CVD benefit

Answer 2

DPP4 inhibitory

Question 3

_____ and ____ have shown CVD benefit (modest and higher in higher risk groups)

Answer 3

SGLT2i and GLP1a

Question 4

this is the conscientious, explicit and judicious use of current best evidence in making decisions about the care of individual patients

Answer 4

evidence based medicine

Question 5

describe the hierarchy of evidence

Answer 5

1 = top of hierarchy (best)

1. meta-analysis of randomized control trials (RCT’S)
2. individual RCT
3. observational studies (patient important outcomes)
4. basic research (test-tube, animal/human physiology)
5. clinical experience (non-systematic clinical observation)

Question 6

what are the three factors that affect evidence based medicine (EBM)?

Answer 6

• best evidence
• patient values
• clinical expertise

Question 7

this is one of the three factors that affect EBM ad consists of religious & moral beliefs along with preferences & rights

Answer 7

patient values

Question 8

this is one of the three factors that affect EBM and consists of clinical trials and systematic reviews

Answer 8

best evidence

Question 9

this is one of the three factors that affect EBM and consists of professional judgement and experience

Answer 9

clinical expertise

Question 10

this is just a number, but can help to describe data and help us make decisions. can be descriptive: numerical information about an object or event derived from a sample (study or trial) from a population; can facilitate inferences about a population when only part of those data (sample) are actually observed

Answer 10

statistic

Question 11

what are the three common scales of measurement for variables in medicine

Answer 11

• nominal
• ordinal
• numeric

Question 12

this is the simplest scale of measurement for variables in medicine; data fits into categories with no particular order; there is no actual measurement - just a count; often dichotomous or binary (yes/no; disease/no disease); generally described in percentages or proportions.

Answer 12

nominal

Question 13

this scale of measurement for variables are also called qualitative observations or categorial observations

Answer 13

nominal

Question 14

this scale of measurement for variables has an inherent order to the categories; summary statistic is the median. is often used in assessment of patient risk; different between 2 adjacent categories is not the same throughout the scale (e.g. going from stage 1 to 2 of cancer may not be as severe as going from stage 3 to 4)

Answer 14

ordinal

Question 15

this scale of measurement for variables is also called quantitative observations

Answer 15

numerical

Question 16

this is one of the types of numerical scales; has a value on a continuum (e.g. age, weight, blood pressure)

Answer 16

continuous scale

Question 17

this is one of the types of numerical scales; values are integers (e.g. # of fractures, # of medications)

Answer 17

discrete scale

Question 18

what are the two summary statistics?

Answer 18

mean and standard deviation

Question 19

this is arithmetic average. used with numerical values and not normally with ordinal values

Answer 19

mean

Question 20

what’s the formula for mean?

Answer 20

the sum of x / n
where x is the individual observations and n is the number of observations

Question 21

this is the middle observation when the observations are listed from smallest to largest

Answer 21

median

Question 22

when the number of observations is odd, the median is the middle number, how do you find the median for an even number of observations?

Answer 22

the median is the average of the values on either side of the middle

Question 23

this is the value that occurs most frequently

Answer 23

mode

Question 24

this kind of graph occurs when outlying values are small; mean < median

Answer 24

left/negatively skewed

Question 25

this kind of graph occurs when outlying values are large; mean > median

Answer 25

right/positively skewed

Question 26

what occurs when the mean and median are similar with regards to a graph?

Answer 26

symmetric distribution

Question 27

in what type of graph should you use mean?

Answer 27

symmetric

Question 28

in what type of graph should you use median?

Answer 28

ordinal or numerical data that is skewed

Question 29

what are the different measures in spread?

Answer 29

- range - standard deviation/variance - coefficient of variation - percentiles - interquartile range

Question 30

this is a measure of spread; it is the difference between the smallest and largest observation. minimum and maximum may also be given

Answer 30

range

Question 31

this is the measure of the variation of our data from the mean

Answer 31

standard deviation

Question 32

______ is the statistic before the square root is taken for the standard deviation

Answer 32

variance

Question 33

this is the measure of relative spread; this allows comparison of relative variation of distributions measured on different scales

Answer 33

coefficient of variation

Question 34

what is the formula for the coefficient of variation?

Answer 34

CoV = standard deviation (s)/mean (x-bar) x 100

Question 35

this is the percentage of a distribution that is equal to or below a particular number; median is 50th percentile; physical growth charts for children is a common usage

Answer 35

percentile

Question 36

this is defined as the difference between the 25th and 75th percentile; this describes the middle 50% of the distribution regardless of the shape

Answer 36

interquartile range

Question 37

this is used with mean with symmetric data

Answer 37

standard deviation

Question 38

this is used with median for ordinal data or skewed numerical data

Answer 38

percentiles and interquartile range

Question 39

tabular presentations consist of nominal and ordinal data presented as ________ or ____________

Answer 39

proportions or percentages

Question 40

this type of table facilitates simultaneous examination of multiple distributions e.g. explore bivariate association between gender and surgery

Answer 40

contingency tables

Question 41

what are different ways to organize/visualize numerical data

Answer 41

- stem and leaf plots - five number summary - box plots - grouped frequency tables

Question 42

what does the stem consist of in a stem and leaf plot?

Answer 42

all but the right most digit (e.g. 483, the stem is 48)

Question 43

what does the leaf consist of in a stem and leaf plot?

Answer 43

the right most digit (e.g. 483, the leaf is 3)

Question 44

true or false: the stem of a stem and leaf plot should be written from smallest to largest

Answer 44

true

Question 45

what is the purpose of the stem and leaf plot? (what is it helping us visualize?)

Answer 45

the collection of leaves will have the general shape of the distribution r

Question 46

this helps to show the location and spread of the data; it displays a full range of data (min and max), displays a common range (25th percentile/Q1 and 75th percentile, Q3) and displays a typical value

Answer 46

five number summary

Question 47

in a box plot or box and whisker plot, what are the upper and lower hinges made with?

Answer 47

1st and 3rd quartile

Question 48

in a box plot or box and whisker plot, the _____ is the line that is found within the box

Answer 48

median

Question 49

in a box plot or box and whisker plot, symmetry is evaluated by the symmetry of the hinges with respect to the median; if the hinges are equidistant from the median the data is ____________

Answer 49

symmetrical

Question 50

in a box plot or box and whisker plot, symmetry is evaluated by the symmetry of the hinges with respect to the median; if the upper hinge is further away from the median, the data is ________ skewed

Answer 50

positively

Question 51

in a box plot or box and whisker plot, symmetry is evaluated by the symmetry of the hinges with respect to the median; if the lower hinge is further away from the median the data is ______ skewed

Answer 51

negatively

Question 52

in a box plot or box and whisker plot the spread of data may also be shown by _____; these are drawn from the upper and lower hinges TO the largest/smallest non-outlying values

Answer 52

whiskers

Question 53

in a modified box plot, what is the boundary for outliers?

Answer 53

1.5 x interquartile range from the box

Question 54

group observations on variable are placed into contiguous, non-overlapping _______; this is a term used in statistics when we are given a continuous series.

Answer 54

class interval *class means a group of numbers in which items are placed such as 0-10, 10-20, 20-30. *class interval refers to the numerical width of any class in a particular distribution

Question 55

this indicates how often a specific kind of event occurs within the total number of observations

Answer 55

relative frequency

Question 56

used to determine the number of observations that lie above (or below) a particular value in a data set; the collection of all previous frequencies together

Answer 56

cumulative frequency

Question 57

how can you construct grouped frequency tables?

Answer 57

1. group observations on variable into a continguous, non-overlapping class interval (bins) 2. place each observation into only one bin 3. tabulate frequency of observations in each bin - can calculate relative frequency (proportion/percentage) 4. can also tabulate cumulative frequency

Question 58

what is the general rule for how many class intervals you should have?

Answer 58

5-20

Question 59

grouped frequency distributions are displayed visually as a _________. unlike bar graphs, these are generally joined as they represent a continuous distribution (not frequency of categories)

Answer 59

histogram

Question 60

the area of the bar of a histogram is proportional to the _________

Answer 60

frequency

Question 61

Relative frequencies can also be grouped as a histogram, looks the same, but has a different ___ scale (AUC = 1 or 100%)

Answer 61

Y

Question 62

this is created by linking the mid-points of successive bins.

Answer 62

frequency polygon

Question 63

this is a form of frequency distribution that represents the sum of a class and all of the classes below it

Answer 63

cumulative frequency distribution

Question 64

when this is on the y-axis, it allows us to estimate the median based on looking at the graph

Answer 64

cumulative frequency distribution

Question 65

what is the effect of having larger samples?

Answer 65

larger samples = more observations = more bins = smaller bins