Quantitative 4- Data Analysis

Question 1

As part of the continuing professional development, what is encouraged?

Answer 1

Important in healthcare to be up to date with current research, always read current articles and journals.

Question 2

What did Greenhalgh (1997a, 1997b) provide in his two seminal papers?

Answer 2

• provides two seminal papers on how to interpret statistics in RCT’s, including how researchers cheat to produce results that appear significant.

Question 3

What are the methods used in analysing data?

Answer 3

o	Relative risk 
o	Absolute risk 
o	Odds ratios 
AND
o	Number needed to treat (NNT) to describe the results of a trial.

Question 4

What are the differences in the two styles of analysis?

Answer 4

is one establishes statistical significance and other measures clinical effectiveness.

Question 5

Why do we need statistics?

Answer 5

• Statistics is about dealing with uncertainty and variation and the aim of statistical analysis is to establish that an intervention or medication will work for most people, most of the time.
• This declares that an intervention should demonstrate a real effect at least 95 times out of 100 to be beneficial.
• We know that humans differ in their response to an illness, with some suffering more than others.
• Doctors diagnose patients probabilistically- there is a strong probability for this patient to have this disease.

Question 6

What is essential when collecting data, that needs to be analysed?

Answer 6

-It is essential that the data are collectable in a form appropriate for the study and that they measure what they are supposed to measure otherwise the whole research will be misleading.

Question 7

What are the two elements of discrete outcomes?

Answer 7

• Risk: the probability of something going wrong, and the negative consequences if it does.
• Rate: the actual number of events that occur.

Question 8

What is the other type of outcome measure?

Answer 8

Continuous

Question 9

Average, Mean, Median and Mode

Answer 9

• It is important to use the right measure to compare the control and experimental group.
• Often done by comparing the average or mean of the groups.

Question 10

How can you calculate measures of effect?

Answer 10

• The purpose of a randomised control trial is to determine whether one treatment or intervention is better than the other.
• Can be done by constructing a 2x2 table
• Using this table we can enter the results of trial and calculate relative and absolute risk ratios, odd ratios and NNH.

Question 11

What does risk identify?

Answer 11

-Determine what risk the control group has and what risk the experimental group has of getting the disease.

Question 12

What is experimental event rate? -ALSO REFERS TO CONTROL EVENT RATE (CER)

Answer 12

is a measure of how often a particular statistical event (such as response to a drug, adverse event or death) occurs within the experimental group.
a- being the experimental group that caught the event
b-being the experimental group that did not get the event
EER= a/(a+b).

Question 13

What is relative risk?

Answer 13

is the ratio of the risk of the event in one regimen compared with the risk of an event in another regimen.
The number one is an important number in understanding relative risk.
If the RR=1 the risk of the event is equal in each group
- therefore there is no difference in the risk of event in both treatment.
If the RR= <1 the risk of the event is lower in the experimental group
If the RR= >1 the risk of the event is higher in the experimental group
EER/CER

Question 14

What is odds ratio?

Answer 14

measure off treatment effectiveness.
If the OR= <1 the odds of the event are lower and the treatment effect is better in the experimental group.
If the OR= >1 the odds of the event is higher which means that the control group has the better treatment
(a/b)/(c/d)

Question 15

How can you represent the OR visually?

Answer 15

a forest plot

Question 16

What is the number needed to treat (NNT)?

Answer 16

represents the number of patients who must be treated in order to achieve a result.
Two step calculation:
1. absolute risk reduction (ARR)- absolute arithmetic difference between the CER and EER.
2. NNT= 1/ARR.
meaning that for every NNT with the new vaccine one additional person would be protected compared to the control group.

Question 17

What is number needed to harm (NNH)?

Answer 17

using the same calculation of NNT we can also calculate how harmful a treatment might be and whether the risks outweigh the benefits.

Question 18

What is confidence intervals?

Answer 18

Provides information about the range of the observed effect.

The range of values used to estimate population parameters