Linking analysis methods MEDI6302 Session 3 Linking analysis methods to research questions Sydney Broome Fremantle

question, design & analysis are linked Research question, design & analysis are linked Analysis method Research question Research design © Eric J. Visser 2018 UNDA. All rights reserved V2.0

Analysis method Organises & presents data in systematic & understandable way Tests the data to answer research question (hypotheses) Analysis methods described in methods section of paper Analysed data presented in results section Three main research analysis methods are … © Eric J. Visser 2018 UNDA. All rights reserved V2.0

Analysis methods Qualitative -describes & interprets data Quantitative -e.g. case reports, interviews, diaries Quantitative -organises, tests & presents data mathematically -statistical approach -basis of hypothesis testing Mixed-methods -combination of qualitative & quantitative methods © Eric J. Visser 2018 UNDA. All rights reserved V2.0

Qualitative research Describes & interprets data to identify meanings & patterns, without using mathematics Popular in social sciences No hypothesis testing involved Data gathering: observations, interviews, questionnaires, documents Analysis methods: phenomenology, ethnography, grounded theory Presentation: text, tables, diagrams QR may lead to confirmatory quantitative studies © Eric J. Visser 2018 UNDA. All rights reserved V2.0

Qualitative methods of analysis Phenomenology: in-depth interviews to describe how individuals experience a phenomenon Ethnography: rich & holistic description of the culture of group under study Grounded theory: development of a “bottom-up” theory based on data analysis, often collected by in–depth interviews Case study: detailed accounts of one or more cases © Eric J. Visser 2018 UNDA. All rights reserved V2.0

Learning task 1 Qualitative methods Provide an example of how qualitative research might be used to investigate a medical condition affecting a remote aboriginal community in WA? Provide a historical example of how qualitative research was used to investigate a 19th century health-care problem? © Eric J. Visser 2018 UNDA. All rights reserved V2.0

Quantitative research Descriptive statistics -organises & presents data in a ‘comprehensible’ form -frequency, central tendency (mean, mode median), spread (range, IQR, SD) -presented as tables or graphs (histogram) Comparative statistics -differences between groups ( t-test, Chi square, ANOVA) -associations between groups (correlation, regression) -effect-size (NNT, odds ratio; relative risk, Forest plots) -Basis of hypothesis testing -Statistical significance & power © Eric J. Visser 2018 UNDA. All rights reserved V2.0

Descriptive statistical analysis Learning task 2 Descriptive statistical analysis Understand the role of descriptive statistics in data analysis How is the central tendency of data analysed? Understand the key features of a normal distribution How is the spread of data analysed? Understand interquartile range & ‘box-and-whisker plot’ How are descriptive data presented in a paper? © Eric J. Visser 2018 UNDA. All rights reserved V2.0

Statistical power & sample size Power  probability of detecting a TRUE positive result  probability of accepting a FALSE negative result Power determines the sample size (and vice versa) Affects research design: numbers, timeline, costs Power calculation is always required Power calculation must be reported in methods section Consult a statistician EARLY about power © Eric J. Visser 2018 UNDA. All rights reserved V2.0

Learning task 2 Statistical power What is a type I error (accepting a false positive) What is a type II error (accepting a false negative) What is the α-risk? (p of type I error; or the significance level; 0.05) What is the β-risk? (p of type II error; 0.2) What is 1 - β (Power; 1.0 - 0.2 = 0.8) What 3 factors affect power? Statistical significance level (p <0.05), expected size of outcome, sample size Calculate the sample size required for your research https://www.statisticalsolutions.net/pssZtest_calc.php

End © Eric J. Visser 2018 UNDA. All rights reserved V2.0

Descriptive statistical analysis Data presented as: Tables Histograms Distribution curves Box-and-whisker plots © Eric J. Visser 2018 UNDA. All rights reserved V2.0

Distribution curve Frequency or Probability Outcome © Eric J. Visser 2018 UNDA. All rights reserved V2.0

Distribution curve derived from histogram © Eric J. Visser 2018 UNDA. All rights reserved V2.0

Normal distribution Continuous probability curve of frequency of an outcome © Eric J. Visser 2018 UNDA. All rights reserved V2.0

Power Analysis © Eric J. Visser 2018 UNDA. All rights reserved V2.0