Flashcards in Quantitative - design, sampling and randomisation issues in randomised controlled trials Deck (28)

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1

## What is the basic layout of a RCT?

### study pps --> intervention group and control group --> outcome present in either group? (yes or no)

2

## what is the design of a RCT?

###
-all trials have an intervention

-PPs randomised to either recieve the intervention or not (control group)

-sometimes there's an attention arm (similar to intervention but without 'active' ingredient)

-outcomes of interest = measured

3

## What are hypotheses?

###
-trials frquently start with them

-predictions about what they expect the intervention to achieve

4

## What is a null hypothesis (Ho)?

###
-there will be no difference between the control and intervention arms

-assumed true at the start and has to be disproved

5

## What are variables?

### factors being investigated

6

## What is a dependant variable?

### -often the outcome of interest e.g. healing time

7

## What is an independant variable?

### -the intervention factor e.g. the dressing being used

8

## How else can the IV and DV be described?

### like cause (effect of dressing - IV) and effect (healing time - DV)

9

## How is the population chosen in trial recruitment?

###
-target group researchers are interested in

-must be cleary defined (so know wwho results are applicable to)

-a sample will then be drawn (representative of the population)

10

## What critera do trials have when recruiting?

### inclusion and exclusion

11

## What types of sampling are there?

### probability and non-probability

12

## What is probability sampling?

###
-gives an unbiased sample where everyone who meets the criteria has a chance of selection

-choose the sample of those entering the trial and is different to them being randomly allocated to groups once in the trial

13

## What is non-probability sampling?

### -non-random sampling and the chance of being selected cant be estimated

14

## What are the four types of probability sampling?

### simple random, stratified random, cluster and systematic random

15

## What is simple random sampling?

###
-random selection of everyone in the population list

-rarely done because difficult to get population list

16

## What is stratified random sampling?

### -put in groups according to characteristics (lile gender) then randomly selected

17

## What is cluster sampling?

### -random selection of larger units (like hospitals) which PPs are then randomly selected from

18

## What is systematic sampling?

### -random selection at predetermined intervals

19

## What are the factors affecting sample size?

###
-population factors - similarity of population to each other, expected rate of 'event', expected attrition (loss to study)

-design - number of variables, sampling

-measurement - sensitivity of measures

-practical factors - cost and convenience

20

## What is a power calcuation and when is it performed?

###
-used to calculate the minimum effect sample size that is likely to be detected in a study using a given sample size.

-also used to calculate the minimum sample size required so that one can be reasonably likely to detect an effect of a given size

21

## How are patients allocated to trial groups in RCTs?

###
-usually in a sequence over a period of time

22

## How are patients allocated in to arms of the trial?

### -methods of randomising them into the arms of the trial (intervention or control) are similar to the random selection of the sample

23

## What are the three types of randomisation?

### simple, block, stratified

24

## What is simple randomisation?

### -'tossing a coin' but usually done with random number tables

25

## What is block randomisation?

### -to keep numbers in each group close

26

## What is stratified randomisation?

### -to balance chosen characteristics across the arms of the trial

27

## What does it mean when a trial is single blind?

###
- one person (usually PP) knows which arm of the trial thy are in (e.g. if its obvious what treatment they recieve)

-perosn assessing the outcome doesnt know

28