1. S TATISTICS Dr. Omar Al Jadaan Assistant Professor – Computer Science & Mathematics

2. A GENDA Introduction Organizing & displaying data Summarizing data Probability Normal distribution Tests of significance & hypothesis testing Parametric tests Non-parametric tests Measures of relationship Application of statistics in health sciences Use of computer for data analysis

3. I NTRODUCTION Basic terms and Concepts Meaning and scope of statistics Type and sources of data Levels of measurement scales

4. I NTRODUCTION (C ONT.) Basic terms and Concepts Statistics is a tool in all biological and medical sciences. Why use statistics? Measurements (systolic BP (130-160-130)mmHg Variability (cigarette  lung cancer ) What about passive smokers are they going to have lung cancer Differences are almost bound to occur due to real effect, random variation or both(specifying how much the variation is the art of statistics)

5. I NTRODUCTION (C ONT.) Statistics is about common sense and good design A well-designed study, poorly analyzed can be rescued by reanalysis. Medical statistician task is to ensure the well-design of the study and the results are comparable and generalisable Age, gender, ethnicity The difficulty with observational studies is that there is an infinite source of confounding variables.

6. I NTRODUCTION (C ONT.) Types of Data Statistician gather and process data. Variable QualitativeQuantitative Nominal Unordered (non- over-lapping) Ordinal Ordered Counts Integer Measured (continuous) Gender Blood group Eye color Marital status Diseases Stage Social class Education level Days sick per year Number of pregnancies Weight in Kg Height in Meter Age (in years, hours and minutes)

7. Q UALITATIVE D ATA Nominal data: are data that one can name and put to categories. They are not measured but simply counted They are unordered Binary: yes/no, male/female, cured/not cured, pregnant /not pregnant. Can have more than categories: blood group, country origin, ethnic, eye color, marital status,

8. Q UALITATIVE D ATA Ordinal data: if there are more than two categories of classification it may be possible to order them in some way. After treatment a patient may be either improved, same or worse Woman may never have conceived, conceived but spontaneously aborted, or given birth to a live infant. Education can be none, elementary school, middle school, high school, college and above. Rank where codes of the best, second best, …, worst.

9. Q UANTITATIVE D ATA (N UMERICAL ) Count data: are often count per unit (integer number)( time, month, attacks, person,….) In dentistry we have decayed, filled, missing teeth (DFM).

10. Q UANTITATIVE D ATA (N UMERICAL ) Measured or continuous data: take any value in a given range. Age, body mass index, years of mestruation. Divide a continuous variable into more than two groups to ease the grouping of population.

11. I NTERVAL AND R ATIO S CALES In interval scale (body temperature, calendar dates) the difference between two measurements has a meaning, but the ration does not. The zero value has no meaning. In ratio scale ( body weight, 10% increase implies the same weight increased whether expressed in Kg. or Pound. The zero value has a meaning in ratio scale

12. H OW STATISTICIAN CAN HELP ? Investigator should seek the advice of statistician at the early stage of an investigation. Where the medical statistician can help? Sample size and power considerations Sample size ( finance, time, patients) Questionnaires Choice of sample and control subjects Design of study Laboratory experiments Displaying data Choosing of summary statistics and statistical analysis