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RESEARCH METHODS Quantitative Research by Dr Viv Rolfe. Evidence Based Practice The University of Nottingham School of Nursing. Dr Vivien Rolfe BSc PhD. 20 Year research career Degree - Physiology PhD - Diarrhoeal diseases Research - Inflammatory bowel disease (Great Ormond Street)

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research methods quantitative research by dr viv rolfe

RESEARCH METHODS Quantitative ResearchbyDr Viv Rolfe

Evidence Based PracticeThe University of Nottingham

School of Nursing


Dr Vivien Rolfe BSc PhD

  • 20 Year research career
  • Degree - Physiology
  • PhD - Diarrhoeal diseases
  • Research - Inflammatory bowel disease (Great Ormond Street)
  • Research - dog and cat nutrition (Mars UK)
  • Market research – qual and quant (Mars UK)
  • Lecturer - University of Nottingham
ice breaker needs from today 5mins
Ice Breaker + Needs from today (5mins)
  • Do they know eachother?
  • Everyone say your name, where from and something about yourself.
  • What do they want out of today?
  • Write on board.
plan of today
Plan of Today
  • Introduction to research
  • Qual versus quant
  • Types of quantitative research
research is
Research is…..
  • inquiring into, finding out
  • a systematic investigation to establish facts
  • a search for knowledge
  • “original investigation undertaken in order to gain knowledge and understanding.”

Dept. For Employment and Learning & HEFCE (Higher Education Funding Council for England)

health and medical research
Health and Medical Research
  • Research is fundamental to advancing healthcare and medicine.
    • Produces new treatments and drugs.
    • Advances understanding of new diseases and problems (obesity, aging, CJD, MRSA…all topical).
    • Can help determine best type of care.
    • Can help evolve patient services.
    • Development of diagnostic tests.
    • Development of prognostic markers.
uk medical research priorities
UK Medical Research Priorities
  • DOH - £540m in 2002-2003
  • cancer, mental health, coronary heart disease (CHD)
  • ageing and older people, public health, genetics , diabetes.
think about research 5 minutes in pairs
Think about research? (5 minutes in pairs)
  • List some different types of research you are aware of.
  • Who does it?
  • What is it?
  • Write ideas on post it notes and cluster (hopefully into QUAL and QUANT).
research from dream to reality
Research – from dream to reality


What? Which? Who?

What am I looking at?

Which methods to use?

Who am I investigating?



Literature review





Conduct Research

Data analysis


qualitative versus quantitative
Qualitative versus Quantitative




Big picture

Tests ideas and theories

Generates ideas and theories

Quantify - measure

Opinions, feelings


Subjective (opento personal interpretation)

Numbers and statistics

Words “verbatims”

quantitative research

Quantitative Research

“a formal, objective, systematic process in which numerical data are utilised to obtain information about the world“

types of quant
Types of QUANT


Case study

Cross sectional


Case control





Needs assessment

Information gatheringabout populations.


Human clinical trial

Veterinary clinical trial

Animal experimentation

In vitro laboratory

All test a hypothesisabout an intervention,technique, practice,service.

types of quant study design
Types of QUANT Study Design

4 main types:

  • Clinical trials (from crap to RCT)
  • Cohort studies
  • Case-control studies
  • Cross-sectional studies
clinical trial
Clinical Trial
  • Experimental research testing the effectiveness of an intervention on a sample of human subjects.
  • Called intervention trials.
  • Clinical research usually stems from laboratory-derived ideas and hypotheses:
        • In vivo – whole body
        • In vitro – test tube
what happens in a clinical trial
What happens in a Clinical Trial?
  • People usually do have a disease or illness at the study beginning, they are observed to see the treatment/intervention is having an EFFECT.

“I’m designing a clinical trial and I’ve picked….”

Fred, Harry, Mavis, Bert, Daisy

Tom, Betty, David, Edna, Bill


e.g. brushing teeth using fluoride toothpaste

No Treatment

Measure and compare: e.g.

number of fillings over a year

what do you notice about this study
What do you notice about this study?
  • A and B subjects are hand-picked
  • small numbers (10’s)
  • the groups are different
  • the study is not blind
  • there is no placebo
  • it is one phase (single leg)
pitfalls to overcome
Pitfalls to Overcome


  • A and B subjects are hand-picked - researcher could manipulate the outcome of the research so introduce BIAS (unfairness)
  • The group numbers are small – you must complete a POWER CALCULATION to see how many subjects to use, otherwise statistical analysis will be problematic.
  • The groups are different - one contains children and the other doesn’t, so we are not comparing like with like. Groups must be MATCHED.


  • The study is not blind - means the clinical staff and patients know who is in what group, which causes BIAS.
  • There is no placebo - or “dummy”, so no adequate control.
  • The design has only one leg (ONE PHASE) so may be susceptible to differences due to TIME.
creating a robust trial

Creating a Robust Trial

A and B subjects are hand-picked

small numbers; not matched, not blind, no placebo; one phase (single leg)

A and B are randomly chosen

Groups are matched (age, sex, other)

Single blind (patient doesn’t know)

Placebo controlled

Double blind (patient and clinician don’t know)


Multi-centre (UK, International)

  • Pilot study
  • Not robust evidence
  • Used to get funding/
  • interest for a larger
  • study
  • Large-scale study
  • Evidence to inform
  • clinical/health
  • care decisions
how could you improve the study
How could you improve the study?
  • 10 minutes in groups
  • What do you want to look at?
  • Who would you use?
  • What would you measure?
ideal study
Ideal Study

Toothpaste + placebo

Toothpaste + fluoride


e.g. if study

done at Easteror Xmas, timewill be aninfluence!.



Toothpaste + fluoride

Toothpaste + placebo

Randomly chosen

Larger numbers


Double blind




Randomisation - the random assignment of subjects to treatment groups

Double-blind - neither the researcher or the subjects know which are the experimental group or control group


Cross-over (may be constrained by ethics,but better if each subject acts as their own control which can reduce sample size – butneed a “washout phase” and not appropriate if treatment gives permanent effects)

Multi-centre (may be costly and timely)

what to look for in a good trial
What to Look for in a Good Trial…..
  • Look for these words in the methods section…
  • Randomised-controlled trial (RCT)
  • Double-blind randomised-placebo-controlled trial – THE BEST.
  • RCT’s follow standardised procedures to ensure good scientific standard.
sources of rct evidence
Sources of RCT evidence
  • Cochrane Database of Systematic Reviews
the 3 c s cross section cohort case control

Non-experimental QUANT

The 3 C’sCross-sectionCohortCase-control

Effectiveness of diagnosis or screening

Aetiology or prognosis

Aetiology or prognosis for a rare condition

cross sectional studies
Cross-sectional Studies
  • Look at a relationship in a defined group at ONE POINT IN TIME (not over a period of months/years).
  • Used for testing the effectiveness of diagnostics or screening, or tests for the prevalence of a disease or parameter.
  • May measure a physiological parameter/do a scientific test.
  • Give valuable insight into whether a practice/test needs to be modified to improve health care.

Example 1 Tanning is associated with optimal vitamin D status and higher bone mineral density.

the methods
The Methods
  • Why – Vitamin D is made in the skin in sunlight, so do people who use sunbeds have higher concentrations of vitamin D?
  • What – a cross-sectional analysis of sunbed and non-sunbed users.
  • Who – 50 people who use sunbeds weekly and 106 control non-users.
  • How – compare blood Vitamin D levels, and bone mineral density testing.
the results
The Results
  • Tanning bed users had 90% higher blood vitamin D levels compared to controls.
  • Tanners had significantly higher bone mineral density scores.
the conclusions
The Conclusions
  • Regular use of a tanning bed can benefit the skeleton.
  • OK, there are obvious known additional risks of skin cancer, but this study indicates that sun beds may be of therapeutic use for some conditions.
strengths and weaknesses
Strengths and weaknesses
  • Cheap and simple
  • Ethically safe


  • Establishes an association/relationship between things (UV rays and Vitamin D), but but not causes
  • If it relies on questionnaires, patient recall of events may introduce bias susceptibility
cohort studies
Cohort Studies
  • “Cohort” means group of individuals with similar traits…
    • e.g. same age
    • support same football team (West Ham of course)
    • who all have eczema
why do a cohort study
Why do a cohort study?
  • Often carried out to study harmful interventions (like smoking) which would not be ethically permitted in a clinical study.
  • To see what risk factors contribute to a disease, or see what their outcome or PROGNOSIS is in the future.
  • These are longitudinal studies – over a period of time.
  • Can be prospective - look forward, to look at if a disease develops, or the outlook/prognosis if the disease is already there.
  • Can be retrospective - look backward, to examine the history of a disease, and find risk factors associated with it.
retrospective cohort study
Retrospective cohort study

What were they exposed to?

Clinical Records



1995 - 2005



Risk factors

Possible causes

the methods1
The Methods
  • Why - MRSA infections in football are an increasing problem.
  • What - A retrospective cohort study was carried out to see what factors were contributing to the infections.
  • Who – cohort of 200 football players with skin abscesses or infection were studied.
  • How – their habits/ behaviours/ recorded.
the results the risk factors
The Results – the risk factors
  • The incidence of infection differed depending on the players position (and whether he had more knocks and bumps).
  • Turf burns enhanced the risk.
  • Body shaving enhanced the risk.
  • Sharing the Jacuzzi at the end of the match showed a small increase in risk of developing infection.
the conclusions1
The Conclusions
  • Educate players to reduce body shaving before a game.
  • Improve padding to prevent turf burns.
  • Introduce means of sterilising Jacuzzi water, just as an additional precaution.
  • Probably can’t do much about playing positions.
prospective cohort study
Prospective cohort study

JAN 2005

JAN 2005 – JAN 2006

No Disease



Assessment of risk factors (environment, lifestyle)

Can be clinical measure or a questionnaire

the methods2
The Methods
  • Why - HIV infection leading to AIDS is a major cause of mortality in Africa (and other countries). Observations suggest that circumcision reduces HIV infectivity.
  • What – a prospective cohort study was carried out.
  • Who - 745 Kenyan truck drivers.
  • How – sexual habits were recorded at interview and follow up interviews.
the results1
The Results
  • Prognosis - after intercourse the probability of contorting aids was high.
  • Infectivity was higher for uncircumcised men compared to circumcised men.
the conclusions2
The Conclusions
  • Lack of circumcision does appear to be a risk factor in AIDS transmission.
  • Encourage circumcision if culturally possible, or promote awareness of this fact to modify sexual behaviour.
strengths of cohort studies
Strengths of Cohort Studies
  • Looks at more than one influence or factor compared to clinical trial that just studies one (e.g., using the Jacuzzi, turf burns, player’s game position).
  • Provides rich information about lifestyle and health associated RISK FACTORS.
  • Ethically safe (i.e. not inflicting treatments on people).
  • Easier and cheaper than an RCT.
weaknesses of cohort studies
Weaknesses of Cohort Studies
  • In order to observe any statistical and biological effects it is often necessary to study large groups.
  • Large studies are costly and timely, particularly the prospective ones.
  • Blinding is difficult – i.e. the subjects know what group they belong to, so is often best not to tell them the nature of the study.
  • No good for rare diseases where large groups don’t exist.
  • Often relies on people’s recollections.
case control studies
Case-control studies
  • Similar to cohort in being able to identify risks.
  • Rather than looking at random groups, smaller numbers of patients (cases) are chosen along with a CONTROL.
  • Because patients are chosen, this can introduce bias either from who is selected, and how the measurements are taken.
  • However, you can focus in on rare cases or situations.
case control studies1
Case control studies
  • Answers the question “what makes a group of individuals different in terms of the causes of a disease”?
  • Design: Can be prospective or retrospective looking back at medical history.
  • Needs 2 groups - Compares those with the disease with a control group of people with similar characteristics (but no disease).
the methods3
The Methods
  • Why - the prevalence (occurrence) of stomach cancers in some parts of India is increasing. It is not known what factors are associated with this.
  • What – a prospective case-control study monitored the risks of developing stomach cancer.
  • Who - 194 patients and a matched (age, sex, religion) healthy control group for 3 years.
  • How – interviews using questionnaire.
the results2
The Results
  • A questionnaire collected data on food intake, socio-demographic factors and other behaviours such as smoking.
  • Risk of cancer was high for those eating spicy food, consuming chilli, and consuming high temperature food.
the conclusions3
The Conclusions
  • Some interesting associations have been found between diet and cancer.
  • Further studies are needed to see whether there is a definite link between spicy food and stomach cancer (ie now go back to the lab and test this hypothesis).
strengths and weaknesses1
Strengths and weaknesses
  • Quick and cheap
  • The only feasible method for very rare disorders fewer subjects needed than cross-sectional studies


  • Often relies on recall to determine result
  • Difficult to select a control group which may introduce bias
types of quantitative research
Types of Quantitative Research

4 main types:

  • Clinical trials (from crap to RCT)
  • Cohort studies
  • Case Control study
  • Cross-sectional studies


From the handout distinguish which of the following are:
    • 1. Clinical trial (is it a “good” or “bad” one?
    • 2. Cohort studies
    • 3. Case control studies
    • 4. Cross-sectional studies
studies cited in this course
Studies Cited in this Course

Tangpricha V, Turner A, Spina C et al. Tanning is associated with optimal vitamin D status (serum 25-hydroxyvitamin D concentration) and higher bone mineral density. Am J Clin Nutr, 2004, 80(6), 1645.

Begier EM, Frenette K, Barrett NL et al. A high-morbidity outbreak of MRSA among players on a college football team, facilitated by cosmetic body shaving and turf burns. Clin Infect Dis, 2004, 15;39(10), 1446.

Mathew A, Gandadharan P, Varghese C et al. Diet and stomach cancer: a case-control study in South India. Eur J Cancer Prev, 2000, 9(2), 89.

Baeten JM, Richardson BA, Lavreys L et al. Female-to-male infectivity of HIV-1 among circumcised and uncircumcised Kenyan men. J Infect Dis, 2005, 15;191(4), 546.

useful weblinks
Useful Weblinks

Medline – the one-stop resource for all global medical and health research.

For example to find a type of study type in “case control” “cohort”, etc. You can alsouse the “limits” button to search for an RCT or a particular population group.

glossaries of research terms
Glossaries of Research Terms

For quick reference to research terms such as prognosis, prevalence, subjective, cohort, cross-section, statistics, then go to:


No. of cases

Prevalence =


  • Measure of a condition in a population
    • At a point in time
    • Over time (e.g. 1 year)
  • Gives an indication of the extent of a problem and health care requirements.

No. of NEW cases

Incidence =

Population or subpopulation

  • Number of new occurances of a condition
  • over time (e.g. 1 year, 10 years.)
  • Gives an indication of the extent of a problem and health care requirements.

Incidence = 2 out of 22 = 9%

Prevalence 4 out of 20 = 20% in the last 10 years.

1995 - 2005


Experimental Non-experimental

Intervention of drugor practice

Diagnosis or

Screening test





Summarise your own learning here…..


(case controlfor rare groups)


(case controlfor rare groups)



Clinical trial



Session Feedback for Viv Rolfe, EBL Course, Monday 24th January

Please tick which box you think (1 = strongly agree to 5 = strongly disagree)


  • 2 3 4 5





a) The course content reflected the aims andthe expected learning outcomes.

b) The pace was about right.

c) The strong points of the course were (please indicate)

d) The weak points of the course were (please indicate)


  • 2 3 4 5





a) She was knowledgeable

b) She could answer questions satisfactorily

c) She/the course kept my attention.

d) I felt able to participate.


Session Feedback for Viv Rolfe, EBL Course, Monday 24th January

Please tick which box you think (1 = strongly agree to 5 = strongly disagree)

Event Materials

  • 2 3 4 5





a) The handouts complemented the course.

b) The handouts aided understanding.

c) I shall use the website.


  • 2 3 4 5





a) The course was useful.

b) Please rate you understanding/level of knowledge on the subject of research methods:

Before today

Low 1 2 3 4 5 High

After today

Low 1 2 3 4 5 High

c) Any other comments


website and contact details
Website and contact details

Additional information, links to the glossariesand other websites mentioned can be found on Viv’s website

Password is einstein

You can also contact me by email if you have any further questions orcomments