Week 4

Question 1

observational study designs

Answer 1

investigator measures or records events but does not intervene

Question 2

descriptive study designs

Answer 2

ecological and case study designs

Question 3

analytical study designs

Answer 3

cross sectional
case control
cohort

Question 4

ecological studies

Answer 4

at least one variable (exposure/outcome) measured at group not individual level

Question 5

S ecological studies

Answer 5

useful for generating hypotheses

compare same population at different times or at different places in same time

Question 6

L ecological studies

Answer 6

ecological fallacy
associations not causations
link between exposure and effect at the individual level can’t be made

Question 7

ecological fallacy

Answer 7

inappropriate conclusions are made about individuals from aggregated group data

Question 8

cross sectional

Answer 8

defined population is observed at a single point in time or time interval and exposure and outcome are determined simultaneously

Question 9

S cross sectional

Answer 9

data on all variables collected only once
can investigate multiple exposures at once
measures prevalence

Question 10

L cross sectional

Answer 10

unable to measure incidence, only prevalence
unable to determine temporality
not suitable for rare diseases
difficult to identify causation

Question 11

case control

Answer 11

two samples are selected, one case one control
look back and determine how many from each group have the risk factor
retrospective

Question 12

S case control

Answer 12

investigates causes of disease (especially rare disease)

easy, fast, cheap

Question 13

L case control

Answer 13

identifying and enrolling control subjects can be difficult

increased probability of recall bias, selection bias and measurement error since retrospective

Question 14

prospective cohort study

Answer 14

start with people free from disease who are exposed/unexposed to factors
baseline data collected
see how many people develop the disease in each group

Question 15

retrospective cohort study

Answer 15

investigators jump back in time to identify a useful cohort which was initially free of disease and at risk
then use whatever records are available to determine each subject’s exposure status at beginning of observation period and ascertain what happened to the subjects in these exposure groups

Question 16

S prospective cohort study

Answer 16

identify temporality

good for rare exposures and common outcomes

Question 17

L prospective cohort study

Answer 17

selection bias
loss to follow up
insufficient for rare diseases

Question 18

double dummy approach

Answer 18

participants receive both active drug and placebo at different times in study

Question 19

field trials

Answer 19

aimed at disease free people in population but are at risk

aim to evaluate interventions and prevention to reduce specific exposures

Question 20

community trials

Answer 20

community or clusters are defined by treatment groups and examined

Question 21

allocation concealment

Answer 21

those responsible for recruiting participants must not know what groups they will be allocated to; 3rd party required

Question 22

smaller the SE

Answer 22

the more precisely the population mean is being estimated

Question 23

SE AKA

Answer 23

value for the spread for the sampling distribution

Question 24

df

Answer 24

number of independent pieces of information available to estimate another piece of information

Question 25

CLT

Answer 25

For a large sample size, the distribution of the sample mean is normally distributed, even when the population distribution from which the sample has been drawn is decidedly non-normal, with mean equal to the true mean of the sampled population and the SD equal to the SE of the sample mean

Question 26

sampling- unknown true SD

Answer 26

use t score and t table

Question 27

sampling- known true SD

Answer 27

use z score and normal distribution table

Question 28

pyramid of evidence from best to worst

Answer 28

meta analysis 
RCT 
cohort study 
case control 
cross sectional 
ecological 
case series 
case report

Question 29

if describing the spread of observations in a study

Answer 29

use SD

Question 30

if using a sample to infer the population results

Answer 30

use SE

Question 31

If you draw a large sample from this population what should be the shape of this variable (Y) in the sample

Answer 31

same as sample population

Question 32

For large sample what will be the shape of the sampling distribution for the sample mean

Answer 32

normally distributed