BEPH_Lesson06a.pdf

Statistics in a nutshell Biostatistics, Epidemiology and Public Health Fernando Cánovas Bachelor’s Degree in Dentistry TOC Introduction Variables Types Distribution Graphical representations Tendency of data Standard deviation Summaries 2 Statistics Quotes 1. Antibiotics reduce the duration...

Statistics in a nutshell Biostatistics, Epidemiology and Public Health Fernando Cánovas Bachelor’s Degree in Dentistry TOC Introduction Variables Types Distribution Graphical representations Tendency of data Standard deviation Summaries 2 Statistics Quotes 1. Antibiotics reduce the duration of viral throat infections by 1-2 days 2. 5 % of women aged 30-49 consult their GP each year with heavy menstrual bleeding 3. At our health centre, 50 patients were diagnosed with angina last year 2 Statistics What are they? science of assembling and interpreting numerical data (Bland, 2000) discipline concerned with the treatment of numerical data derived from groups of individuals and things (Armitage et al., 2001) 2 Statistics Data items of information plural 2 How is the oral hygiene in citizens of Murcia? brush one’s teeth 3 times a day 2 How is the oral hygiene in citizens of Murcia? brush one’s teeth 3 times a day 2 How is the oral hygiene in citizens of Murcia? brush one’s teeth 3 times a day 2 How is the oral hygiene in citizens of Murcia? brush one’s teeth 3 times a day 2 How is the oral hygiene in citizens of Murcia? brush one’s teeth 3 times a day 2 How is the oral hygiene in citizens of Murcia? brush one’s teeth 3 times a day 2 How is the oral hygiene in citizens of Murcia? brush one’s teeth 3 times a day 2 How is the oral hygiene in citizens of Murcia? brush one’s teeth 3 times a day 2 Statistics Basic terminology population complete set of specimens or objects (statistical units) which can be studied sample subset of a population attribute characteristic of an specimen or object variable logical set of attributes statistic quantity calculated from a sample parameter true quantity in a population 2 Variables Types qualitative or categorical non-measurables nominal - without order ordinal - with order binomial - only 2 categories (boolean) quantitative or numerical measurables discrete - finite, isolated values continuous - infinite, scale, intervals 2 Statistics Variables Ind 1 2 3 ... 200 Sex F M M ... F Diet prot hyd prot ... lip Hygiene high none low ... medium Smoker yes no yes ... yes ... Caries 3 3 2 ... 1 TA 65.9 65.0 59.4 ... 83.7 Age 18 42 25 ... 49 quantitative or numerical discrete - caries, age continuous - TA qualitative or categorical nominal - sex (dichotomous), diet (polytomous), smoker (binary) ordinal - hygiene (polytomous) 2 Variables Distributions percentage of specimens or objects that fall into each category or interval 2 Variables Distributions bar plot 2 Variables Distributions pie chart 2 Variables Discrete distributions 2 Variables Continuous distributions histogram 2 Variables Tendency of data 2 Variables Tendency of data 2 Variables Standard deviation mean deviation =3 2 Variables Standard deviation σ= qP (x−x)2 (n−1) mean deviation = 3 2 Variables Standard deviation σ= qP (x−x)2 (n−1) mean deviation = 3 2 Variables Standard deviation σ= qP (x−x)2 (n−1) mean deviation = 3 2 Variables Standard deviation 2 Variables Standard deviation 2 Statistics Summaries 2 Variables Summaries 2 Refreshing concepts Statistics population mean square sum variance standard deviation P µ = NX P 2 P d = (X − µ)2 σ2 = σ= d2 N P qP d2 N sample P M = Nx P 2 P d = (x − M)2 S2 = d2 N−1 P quasivariance qP d2 S = N−1 2 Bibliography Detels R., Gulliford M., Abdool Karim Q., and Tan C. (2017). Oxford textbook of global public health (Sixth). Oxford University Press. DOI: 10.1093/med/9780199661756.001.0001 2 UCAM Universidad Católica de Murcia © UCAM