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Zekeriya Aktürk, Prof.

Atatürk University Medical Faculty, Class 1

25.10.2010, Erzurum

BiostatisticsBiostatistics

IntroductionIntroduction

http://aile.atauni.edu.tr

zekeriya.akturk@gmail.com

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Aims – Objectives • At the end of this lecture, the participants should

defend the importance of research and have basic information about research and biostatistics.– Name the steps of research

– Formulate an answerable clinical question

– Classify types of data

– Mention features of a data

– Classify different types of studies

– Explain cohort, case control, and randomized controlled studies

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Lets do a study together

AU Medical Faculty Students and Research

Aktürk Z. Erzurum. October 25, 2009

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Bir literatür

Askew, DA. et al. GPs involvement in and attitudes to research. Med J Aust 2002;177(2):74-77

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Stages of a study

1. Ask a question

2. Is the question already answered?

3. Formulate hypothesis

4. Design the method

5. Apply

6. Perform analysis

7. Discussion

8. Report

Tyler CW, Epidemyology

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Most important: idea

My research panel

Idea Method Application Report1. Knowledge and use

of the public on herbal remedies

2. Effect of constipation on cognitive functions

3. .

1. Medical specialty training in Turkey

2. .

1. Effect of structured exercise on weight loss

2. .

1. Osteoporosis prevalence among women in Edirne

2. .

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How to gather ideas?

• Clinical practice

• Work environment

• Ideas from patients

• Colleagues

• Unexpected health outcomes

• …

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Answerable clinical question•Patient/problem Hasta/problem•Intervention Girişim•Comparison Karşılaştırma•Outcomes Sonuç/Çıktı

Is there any difference among a calorie diet and a glycemic diet in decreasing body mass index of obese women?

Centre for EBM http:www.cebm.net/

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Is your question answered?

• Literature search

• Teachers

• Colleagues

• Books

• Internet

• …

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Formulating a hypothesis

• H0 – There is no difference between a calorie diet and a

glycemic diet in decreasing body mass index of obese women?

• H1 – There is a difference between a calorie diet and a

glycemic diet in decreasing body mass index of obese women?

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Types of studies(How to answer the question?)

• Observation– Case report– Prevalance– Case control– Cohost studies– Qualitative studies

• Intervention– Randomized controlled studies

• Methodologic– Validity– Reliability

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Case control study

Cases Controls

Exposed Not exposed Exposed Not exposedT

IME

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Cohort study

Diseases Healthy

Exposed Not exposed

T I M

EDiseased Healthy

Population

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Randomized controlled study

Sick Improved

A therapy B therapy

T I M

E

Sick Improved

Population

Randomization

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Statistical analysis

• Features of data– Current– Reliable– Correct– Complete– Appropriate to use– Appropriate for aim

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Statistical analysis

• Frequency distribution• Importance tests (hypothesis tests)

– Student t-test– ANOVA– Chi square– Mann-Whitney U test– McNemar test– Wilcoxon – Fisher exact test– …

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Lets do an example

• Stages of a study1. Ask a question

2. Is the question already answered?

3. Formulate hypothesis

4. Design the method

5. Apply

6. Perform analysis

7. Discussion

8. Report

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Ask a question

• Is there any difference in recognizing “thyme” between class 1 and class 6 medical students?

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Was the question answered?

• Aktürk Z ve ark.– Medical students have problems in recognizing

herbs. Class six students are better in recognizing.

Genel Tıp Derg 2003;16(3):101-106

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Hypothesis

• H0: There is no difference in recognizing “thyme” between class 1 and class 6 medical students?

• H1: There is a difference in recognizing “thyme” between class 1 and class 6 medical students?

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Method

• The following picture was shown to students from class 1 and 6 by a data projector

Statistics – Frequency distribution

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Kekik resmini tanýdý mý

115 63,2 63,5 63,5

66 36,3 36,5 100,0

181 99,5 100,0

1 ,5

182 100,0

Hayýr

Evet

Total

Valid

SystemMissing

Total

Frequency Percent Valid PercentCumulative

Percent

SINIF

115 63,2 63,2 63,2

67 36,8 36,8 100,0

182 100,0 100,0

1

6

Total

ValidFrequency Percent Valid Percent

CumulativePercent

Statistics – hypothesis testing

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SINIF * Kekik resmini tanýdý mý Crosstabulation

101 14 115

87,8% 12,2% 100,0%

14 52 66

21,2% 78,8% 100,0%

115 66 181

63,5% 36,5% 100,0%

Count

% within SINIF

Count

% within SINIF

Count

% within SINIF

1

6

SINIF

Total

Hayýr Evet

Kekik resmini tanýdýmý

Total

Chi-Square Tests

80,317b 1 ,000

77,468 1 ,00084,089 1 ,000

,000 ,000

79,874 1 ,000

181

Pearson Chi-Square

Continuity Correctiona

Likelihood RatioFisher's Exact Test

Linear-by-LinearAssociationN of Valid Cases

Value dfAsymp. Sig.

(2-sided)Exact Sig.(2-sided)

Exact Sig.(1-sided)

Computed only for a 2x2 tablea.

0 cells (,0%) have expected count less than 5. The minimum expected count is24,07.

b.

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Conclusion

• While 12% of class 1 students correctly recognized thyme, this was 78% in class 6.

• Although class 6 students are better in recognizing thyme, still 22% are not successfull in recognizing.

• There is a significant difference between class 1 and 6 students in recognizing thyme (p<0,001).