Biostatistics Ibrahim Altubasi, PT, PhD The University of Jordan

Statistics The study of statistics involves math and relies on calculations of numbers But, it relies heavily on how the numbers are chosen and how the statistics are interpreted Examples: o A new advertisement for iceberg ice cream introduced in late may of last year resulted in 30% increase in the sales for the following 3 months, thus the advertisement was effective. o 75% more interracial marriages this year than 25 years ago, thus our society accept interracial marriages

Statistics Those examples show that statistics are not only facts and figures Statistics refers to a range of techniques and procedures for analyzing, interpreting, displaying, and making decisions based on data.”

Statistics Statistics are every where o Health, law, psychology, business, sport etc.. They seem to add credibility o E.g. in the TV advertisement It is important to study statistics to become a consumer of research and understand the evidence of our practice

Usually a study begins with inquiry which is Transformed into appropriate research question(s) Usually a study begins with inquiry which is Transformed into appropriate research question(s) Descriptive Question Descriptive Question Relational Question How heavy are class members on average? What is the average study time for students in PT department? What proportion of PTs are bachelor degree holder? Etc…? How heavy are class members on average? What is the average study time for students in PT department? What proportion of PTs are bachelor degree holder? Etc…? Are rehab students less anxious about statistics? Do females achieve higher grades in PT exams? Does quadriceps stretching increase ROM of knee OA? Etc… ? Are rehab students less anxious about statistics? Do females achieve higher grades in PT exams? Does quadriceps stretching increase ROM of knee OA? Etc… ?

Once a research question has been specified, you can distinguish three critical facets of research Design Analysis Measurement Who will be the population? Who will be actually studied? How will the people who are studied be selected? What key variables will be observed or measured in the research? Who will be the population? Who will be actually studied? How will the people who are studied be selected? What key variables will be observed or measured in the research? Population: The entire group that a researcher wishes to study Population: The entire group that a researcher wishes to study Sample: A set of individuals selected from a population Sample: A set of individuals selected from a population Parameter: a value that describes a population Parameter: a value that describes a population Statistics: a value that describes a sample Statistics: a value that describes a sample Sampling error: The discrepancy that exists between a sample statistic and the corresponding population parameter. Sampling error: The discrepancy that exists between a sample statistic and the corresponding population parameter.

Once a research question has been specified, you can distinguish three critical facets of research Design Analysis Measurement Who will be the population? Who will be actually studied? How will the people who are studied be selected? What key variables will be observed or measured in the research? Who will be the population? Who will be actually studied? How will the people who are studied be selected? What key variables will be observed or measured in the research? Sampling procedure: The way to select the sample from the population Sampling procedure: The way to select the sample from the population population Sampling procedure Sample Sample statistic Random Sample? Convenience Sample?

Sampling The process of selecting individuals Random Sample o Every member of the population has equal chance of being selected. o Additionally the selection of one member must be independent of the selection of every other member Convenience Sample Subjects are selected because of the convenient accessibility and proximity to the researcher

Once a research question has been specified, you can distinguish three critical facets of research Design Analysis Measurement Who will be the population? Who will be actually studied? How will the people who are studied be selected? What key variables will be observed or measured in the research? Who will be the population? Who will be actually studied? How will the people who are studied be selected? What key variables will be observed or measured in the research? A Variable is a characteristic or condition that changes or has different values for different individual. A Constant is a characteristic or condition that does not vary but is the same for every individual. A Variable is a characteristic or condition that changes or has different values for different individual. A Constant is a characteristic or condition that does not vary but is the same for every individual. Types of Variables Qualitative vs. Quantitative Qualitative vs. Quantitative Continuous vs. Discrete Continuous vs. Discrete Dependent vs. independent Dependent vs. independent

Type of Variables Qualitative: a characteristic that could be placed into a well defined group or category that do not depend on order (categorical variables) Quantitative: a characteristic that could be measured in terms of numbers Independent variable: is the one which could be manipulated by experimenter Dependent variable: is a variable that is affected during an experiment Discrete: the one measured with exact point on a scale Continuous: the one measured with no discrete points on a scale

Once a research question has been specified, you can distinguish three critical facets of research Design Analysis Measurement Who will be the population? Who will be actually studied? How will the people who are studied be selected? What key variables will be observed or measured in the research? Types of research design Who will be the population? Who will be actually studied? How will the people who are studied be selected? What key variables will be observed or measured in the research? Types of research design The Concept of Control Random assignment Holding other variables constant The Concept of Control Random assignment Holding other variables constant Experimental Design Quasi-experimental design Observational Design

Is random assignment used? Is random assignment used? Yes No “true” experimental Are there multiple groups or measures? Are there multiple groups or measures? Yes No Quasi- experimental Observational

Once a research question has been specified, you can distinguish three critical facets of research Design Analysis Measurement How will data on key variables be collected? How do we ensure valid observation and measurement? How do we ensure that the data are collected precisely and reliably? How will the data be coded for analysis? Which variables are outcomes, and which are predictors? ….? How will data on key variables be collected? How do we ensure valid observation and measurement? How do we ensure that the data are collected precisely and reliably? How will the data be coded for analysis? Which variables are outcomes, and which are predictors? ….? Nominal Ordinal Interval Ratio Scale

Once a research question has been specified, you can distinguish three critical facets of research Design Analysis Measurement NominalOrdinalIntervalRatio True ZeroNo Yes Equal unit difference No Yesyes OrderNoYes

Once a research question has been specified, you can distinguish three critical facets of research Design Analysis Measurement How will data be analyzed to address the research question? How will findings be communicated to other researchers, practitioners and policy-makers? …? How will data be analyzed to address the research question? How will findings be communicated to other researchers, practitioners and policy-makers? …? Data: the complete set of variables / measurements AgeGenderKnee ROM

Once a research question has been specified, you can distinguish three critical facets of research Design Analysis Measurement How will data be analyzed to address the research question? How will findings be communicated to other researchers, practitioners and policy-makers? …? How will data be analyzed to address the research question? How will findings be communicated to other researchers, practitioners and policy-makers? …? Descriptive Statistics: statistical procedures used to summarize, organize, and simplify data Descriptive Statistics: statistical procedures used to summarize, organize, and simplify data Inferential Statistics: procedures that allow us to study sample and make generalizations about the populations from which the samples were selected. Inferential Statistics: procedures that allow us to study sample and make generalizations about the populations from which the samples were selected.