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Zekeriya Aktürk, Prof.

Atatürk University Medical Faculty, Class 1

25.10.2010, Erzurum

BiostatisticsBiostatisticsIntroductionIntroduction

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 togetherAU 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 question2. Is the question already answered?3. Formulate hypothesis4. Design the method5. Apply 6. Perform analysis7. Discussion8. Report

Tyler CW, Epidemyology

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Most important: ideaMy 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 question2. Is the question already answered?3. Formulate hypothesis4. Design the method5. Apply 6. Perform analysis7. Discussion8. 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 63,566 36,3 36,5 100,0

181 99,5 100,01 ,5

182 100,0

HayýrEvetTotal

Valid

SystemMissingTotal

Frequency Percent Valid PercentCumulative

Percent

SINIF

115 63,2 63,2 63,267 36,8 36,8 100,0

182 100,0 100,0

16Total

ValidFrequency Percent Valid Percent

CumulativePercent

Statistics – hypothesis testing

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SINIF * Kekik resmini tanýdý mý Crosstabulation

101 14 11587,8% 12,2% 100,0%

14 52 6621,2% 78,8% 100,0%

115 66 18163,5% 36,5% 100,0%

Count% within SINIFCount% within SINIFCount% within SINIF

1

6

SINIF

Total

Hayýr Evet

Kekik resmini tanýdýmý

Total

Chi-Square Tests

80,317b 1 ,00077,468 1 ,00084,089 1 ,000

,000 ,00079,874 1 ,000

181

Pearson Chi-SquareContinuity Correctiona

Likelihood RatioFisher's Exact TestLinear-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).