Theme 9

Question 1

what is EBHC

Answer 1

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

Question 2

what does EBHC take into consideration (4)

Answer 2

1. contextual factors
2. health worker’s expertise acquired through clinical practice and experience
3. current best evidence obtained from clinically relevant research
4. patient values

Question 3

Importance of synthesizing evidence (5)

Answer 3

1. Need to qualify outcomes
2. Many effective tx(alternatives)
3. Costs
4. Info overload/ need for synthesis
5. Changing patient-physician relationship

Question 4

aim of reviews (4)

Answer 4

Readable summary of all evidence
Unbiased reporting of evidence
Transparency
Up-to-date

Question 5

Narrative Review

Answer 5

• Qualitative, narrative summary of evidence on a given topic
• Written by expert in field (generally)
• Typically involve informal and subjective methods to collect and interpret info

(think of what we did in our pharm project)

Question 6

Systematic review definition

Answer 6

Summary of literature that uses explicit and reproducible methods to systematically search, critically appraise, and synthesize on a specific issue. It synthesizes the results of multiple primary studies related to each other by using strategies that reduce biases and random errors””

Question 7

Need for systematic review

Answer 7

• efficient way to access the body of research ( saves time , critical appraisal, interpretation of results)
• explore dif btwn studies
• reliable basis for decision making
• clearly stated objectives and question
• pre-defined eligibility criteria
• comprehensive systematic review
• explicit, reproducible methods
• assessment of validity of included studies

Question 8

Types of bias minimized by a systematic review

Answer 8

publication / language/ indexing/file-drawer

Question 9

Application of meta-analysis (3)

Answer 9

Intervention – estimate efficacies and risk of TX
Diagnostic tests – provide more reliable estimates of diagnostic accuracy of test
Epidemiology – to provide more reliable estimate of risks

Question 10

what is statistics (definition)

Answer 10

“Statistics is the science of collecting, summarizing, presenting and interpreting data, and of using data to estimate the magnitude of associations and test hypotheses.”

Question 11

types of statistics

Answer 11

1. Descriptive statistics

2. Analytic statistics

Question 12

Descriptive statistics

Answer 12

Methods to summarise and present data

Question 13

Analytic statistics

Answer 13

Methods to test associations and draw inferences from the sample to a population

Question 14

Why we need statistics (3)

Answer 14

• Statistics is a way of handling variability.
• It allows us to separate out the real effect from that which could have happened due to chance variability (random error).
• It allows us to make inferences about a larger population from a smaller sample

Question 15

types of variables ( 2 main types and 5 subtypes)

Answer 15

Categorical variables

a. Nominal
b. Ordinal
c. Binary

Numerical / Quantitative variables

a. Discrete
b. Continuous

Question 16

Nominal variables

Answer 16

Categorical variable

Categories in no order, are identified by name
e.g. gender, marital status, ethnic group

Question 17

Ordinal variables

Answer 17

Categorical variable

There is some order and can be recorded in categories
e.g. socio-economic status, severity of a disease

Question 18

Binary variables

Answer 18

Categorical variable

Binary (or dichotomous)-
Variables that have only two possible categories
e.g. alive or dead, smoking status

Question 19

Discrete variables

Answer 19

Numerical / Quantitative variable

Can only take on certain values - value is counted not measured
e.g. count of events, count of people

Question 20

Continuous variables

Answer 20

Numerical / Quantitative variable

Can take on any value - value is measured not counted
e.g. height, blood pressure, CD4 count

Question 21

Rates/ proportions vs ratios

Answer 21

Rates or proportions relate the number of cases to the size of the population at risk
Ratios used to compare two rates or proportions

Percentage of each response sometimes shown as a proportion- Proportion ranges from 0 to 1

Question 22

Summarising and presenting Categorical Data

5 ways

Answer 22

1. Frequency table (Count the number of observations in each category)
2. 2 by 2 tables (show associations between two categorical variables)
3. Measures of the strength of association
4. risk ratio
5. odds ratio

Question 23

Measures of the strength of association

Answer 23

often 2 X 2 table

• Many epidemiological studies set out to investigate the association between an exposure and an outcome (usually disease)
• binary variables (yes or no)

Question 24

Relative risk/Risk ratio

Answer 24

• Compares the risk of outcome in two groups
• Groups can be differentiated by demographic factors or by exposure to a suspected risk factor or treatment intervention
• Used in cohort studies and cross sectional studies

Question 25

interpretation of risk ratio results

Answer 25

* RR = 1 (risk among exposed group = risk among non-exposed i.e. no association) * RR > 1 (exposure is a risk factor) * RR < 1 (exposure is protective)

Question 26

Odds ratio

Answer 26

* The odds of an event calculated from the probability of occurrence * Used in case control studies and cohort studies

Question 27

interpretation of odds ratio results

Answer 27

Calculate the probability of exposure amongst the diseased (cases) vs. the non-diseased (controls) •Odds ratio = 1 (odds are similar) •OR > 1 (exposure is a risk factor) •OR < 1 (exposure is protective)

Question 28

graphing Categorical Data (3 ways)

Answer 28

1. bar chart 2. cluster bar chart 3. pie chart

Question 29

Simple bar graph

Answer 29

* Used to display data from one variable table * Each value or category is represented by a bar * The length of the bar is proportional to the number of events in that category * Makes it easy to compare the relative size of the different categories * Bars can be presented either horizontally or vertically

Question 30

Cluster bar graph

Answer 30

show association between two categorical variables

Question 31

Pie chart

Answer 31

* For categorical variables with more than 2 categories * Where total percentage adds up to 100% * Not very scientific

Question 32

what graphical display of numerical data detects (4)

Answer 32

* Strange values * Patterns * Relationships * Whether intended statistical analyses are appropriate

Question 33

what we use for graphical display of numerical data

Answer 33

Symmetry of data detected in: •histograms •Box plots Relationships detected through: •Bivariate (or scatter plots)

Question 34

Scatter plot

Answer 34

* Used to plot two continuous numerical variables against one another (e.g. height and weight) * Used to explore the relationship between variables * Compact pattern indicates high correlation * Drawing the scatter plot should precede a statistical analysis * Plot one variable on the X-axis and plot the other on the Y-axis

Question 35

Measures of central tendency in Summarising numerical data

Answer 35

1. In symmetrical distributions- Mean 2. in asymmetrical distributions-Median+ Geometric mean 3. Mode

Question 36

Mean

Answer 36

* Arithmetic mean or average | * Useful in symmetrical distributions of data because sensitive to extreme values

Question 37

Median

Answer 37

* The median represents the middle of the set (i.e. half the observations above and half the observations below) * Not sensitive to extreme values -Useful in asymmetrical distributions of data

Question 38

Mode

Answer 38

* The value that occurs most frequently * Useful if we are interested in knowing which values are most popular or to assess whether a measuring instrument has a preference for a certain value * Every set of data has one mean and one median, but could have one mode, no mode, or multiple modes

Question 39

Comparison of mean and median in different distributions

Answer 39

* In normal distribution, mean and median are similar | * In asymmetrical distributions, they are different

Question 40

Measures of variability in Summarising numerical data (3)

Answer 40

1. Range 2. Standard deviation 3. Interquartile range

Question 41

Range

Answer 41

•The largest minus the smallest value or denoted by indicating the smallest and largest value separately

Question 42

Standard deviation

Answer 42

* Gives the average distance from the mean | * Used with symmetrical data

Question 43

Interquartile range

Answer 43

* Used to summarise asymmetrical data (i.e. where there are outliers) * Therefore used with the median * Calculation –75thpercentile minus the 25thpercentile * Gives the range of values between which 50% of the data in the sample lie