STATISTICAL METHODS FOR RESEARCH Programme content This document gives an overview of the content of each screen in the Supervising Doctoral Studies programme. Interactive and/or multimedia elements (e.g. activities, videos) are marked bold. Introduction – Statistics in the context of research Screen Unit 1: Getting started You as a researcher Pre-programme quiz What stage are you currently at? What will I be able to do with my research data by the end of this course? Outline of the programme Notes Defining ‘statistics’ Unit 2: Statistical investigation What is a statistical investigation? Stages 1 to 3 of a statistical investigation Stage 4: Statistical modelling Poll activity: Your familiarity with statistical packages Video interview: Which statistics packages do you use ansd why? Multiple-choice quiz: Yout current knowledge of statistics What types of study are there? What do we mean by ‘statistically valid’? Click to view activity: Randomisation, replication and blocking/stratification Video interviews: o Can you explain your research? o Can you describe your data collecting methods? o Approaching randomisation and blocking (stratification) Download and poll activity: Understanding a model report The aims of this programme Click to view activity: Topics covered in each course Click to view activity: Views on statistics Click to view activity: Examples of the wuantification of variability Matching activity: Definitions of ‘statistics’ Royal Statistical Society definition of ‘statistics’ Classification activity: Headlines with/without statistical information How statistics can help you understand variability in data Click to view activity: Stages of a statistical investigation Click to view activity: Questions about estimates, comparisons and relationships in data Clickable graphic: What a box plot can tell you Two parts of a statistical model Click to view activity: Stages of the statistical modelling process What do these stages mean in practical terms? 1 | Page © Epigeum Ltd, 2014 STATISTICAL METHODS FOR RESEARCH Thinking statistically – Describing data well Screen Unit 1: Describing data well What is a statistical investigation? Summaries for categorical variables Summarising quantitative variables Reflecting the structure in the data The standard deviation Notes Definition of a ‘sample’ Sequencing activity: Steps in the statistical process Types of data Click to view activity: Categorical and quantitative variables One-way tables of frequencies and bar charts Two-way tables of frequencies and bar charts Download and reflection activity: Categorical and quantitative variables and other observations on a dataset The frequency distribution and histogram Click to view activity: Location and variability The quartiles and box plot Notemaking activity: Summarising the quanitative variable Reflection activity: Box plots and outliers Using charts to answer more complex questions Notemaking activity: Commenting on variability Statistical measures of variability (dispersion) based on the actual measurement value Variance Standard deviation Classification activity: Quartiles and standard deviation Empirical rule for the use of the standard deviation Animation: Examples of symmetric and skewed distribution Matching activity: Summary statistics and types of distribution 2 | Page © Epigeum Ltd, 2014 STATISTICAL METHODS FOR RESEARCH Thinking statistically – Making good generalisations Screen Notes Unit 1: Sampling variability and the precision of a sample estimate What use is all this stuff Variability in everyday situations about variability? Click to view activity: What variability means in a practical sense Sampling – the big idea The standard error as a measure of precision of an estimate Fundamental concepts in the modelling approach Sequencing activity: Stages of modelling Sampling in practice Estimation from a sample Animation and notemaking activity: Repeated samples Sampling distribution A conceptual distribution Distribution of sample means vs. distribution of raw data Standard error and standard deviation Click to view activity: Avoiding confusion about the standard error and standard deviation Estimation in practice Video: Worked example of how to obtain a summary output using the Instat statistics package Giving a measure of precision Missing words activity: Summary Unit 2: Using standard errors to build confidence intervals The Normal Video interviews: distribution and o In what ways do you explore the distributions of your datasets? confidence intervals o How do you quantify variability when you present your results? Normal distribution Click to view activity: A graphical representation of the 70-95-100 rule Confidence intervals Click to view activity: Confidence intervals Other distributions: Sampling from a skewed distribution and a binomial distribution Matching activity: Summary Calculating a Click to view activity: Two ways to interpret a confidence interval confidence interval Using software Video: Worked example of how to calculate a confidence interval in Instat How a confidence interval looks graphically Interpretation Video: Worked example of how to calculate a confidence interval in Instat 3 | Page © Epigeum Ltd, 2014 STATISTICAL METHODS FOR RESEARCH Which hypothesis test should I use? Screen Notes Unit 1: Testing the null hypothesis Accepting versus not Cartoon strip: How hypothesis testing works rejecting the null The alternative hypothesis hypothesis A decision-making rule Where p-values come from for hypothesis testing: How to interpret p-values The p-value Statistical significance Video: Using the Minitab statistics package to calculate the p-value and see if it is small enough to reject the null hypothesis Click to view activity: A visual representation of what the p-value quantifies Video: Worked example of conducting a one-sample t-test in Minitab Decision-making: The The significance level 5% significance rule Erring on the side of caution in favour of the status quo Erring on the side of caution against the status quo The effect of the sample size and effect size on hypothesis tests Unit 2: The practice of statistical hypothesis testing Recap Click to view activity: Recap of key learning points about the practice of statistical hypothesis testing Comparing two means Comparing the means from two samples drawn from separate populations Clickable graphic: Table comparing two samples Clarity of the conclusions Reflection activity: Why are the results much clearer for one comparison than for the other? A more general ANOVA (ANalysis Of VAriance) analysis: ANOVA Exploratory stage Further analysis Video: Worked example of how to compare the sample means from multiple samples using the R statistics package What do we mean by practical importance? Which test do I use? Matching activity: Null hypothesis retained vs. null hypothesis rejected Matching activity: Research hypotheses and statistical (null) hypotheses Video interview: o What types of hypothesis tests do you carry out on your data? o What p-value do you consider to be an indicator of statistical significance? Interactive decision tree: Determining which type of hypothesis test you would use for your data 4 | Page © Epigeum Ltd, 2014 STATISTICAL METHODS FOR RESEARCH Statistical modelling Screen Unit 1: Statistical modelling What is a statistical model? The statistical modelling framework Linking a one-sample ttest to the null regression model Notes Straight line regression Straight line regression stage 4: Generalise your results The quadratic regression model Statistical models as adequate summaries Click to view activity: Statistical modelling Video interview: How are you using statistical models in your research? Stages of the statistical modelling framework Click to view activity: Flowchart of the statistical modelling framework Video: Worked example of how to use SPSS to conduct a t-test, fit the null regression model and compare the results Matching activity: How a one-sample t-test relates to the null regression model Book activity: Using the statistical modelling framework How well does the straight line regression model relate the the observed relationship? Interpretation of results: Regression coefficients Intercept of the fitted line Slope (gradient) of the fitted line Stage four: Generalise results Matching activity: Labelling the data in a table Click to view activity: Straight line regression Where are we now? Quadratic model vs. straight line model Video: Worked example of how you fit the quadratic regression in SPSS Interpreting the extended model Conclusion Click to view activity: Summary of the steps completed 5 | Page © Epigeum Ltd, 2014 STATISTICAL METHODS FOR RESEARCH Analysis of categorical data Screen Notes Unit 1: Analysis of categorical data Comparing one single group of categorical binary data with a hypothesised target Testing for association with categorical binary data: Comparing two groups Confidence interval for a true difference between two proportions Testing for association with categorical binary data: Comparing three or more groups Testing for a linear association between a categorical binary outcome and an ordered categorical explanatory variable The logic of testing a proportion of ‘successes’ against a hypothesised target The z-test Click to view activity: Testing the proportion of ‘successes’ against a target value Confidence interval for a true proportion Sequencing activity: Steps for testing a sample proportion against a hypothesised value The effect of small sample size and extreme results on inference for a proportion Reflection activity: The impact of small sample sizes and extreme observed proportions when calculating confidence intervals Equivalence of z-test and Pearson chi-squared test The logic of testing the equality of proportion of ‘successes in two groups Click to view activity: Alternative ways of expressing contrastintg hypotheses Using Minitab to input data, choose two proportions and generate a table of results True or false activity: Observations on the comparison of two groups Confidence interval for a true difference between two proportions Multiple-choice quiz: Scenario-based question The logic of testing the equality of proportion of ‘successes’ in three (or more) groups Worked example including performing a chi-squared test in Minitab Reminder about the alternative hypothesis Classification activity: True or false? Chi squared test for a linear trend in proportions Worked example Matching activity: Tasks required by research hypotheses and suitable hypothesis tests 6 | Page © Epigeum Ltd, 2014