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Dr Zia-Ul-Ain Sabiha At the end of this session the students will be able to Define Statistics Differentiate between Descriptive Statistics and Inferential Statistics Define Biostatistics Discuss the Uses of Biostatistics 9/6/2015 CHS deptt 2 Define Data Sample and Population Variables Measurement variables Types of Data Exercises to summarize the lecture. 9/6/2015 CHS deptt 3 Statistics is science of conducting studies to collect ,organize, summarize, analyze, and draw conclusions from the data. 9/6/2015 CHS deptt 4 A subject that deals with the collection , compilation , presentation , analysis and presentation of data. Drawing inferences about a body of data when only a part of the data is observed. Scientific study of numerical data based on natural phenomenon 9/6/2015 CHS deptt 5 9/6/2015 CHS deptt 6 Descriptive Statistics Consists of the collection , organization , summarization, and presentation of data. Inferential statistics consists of generalizing from samples to populations ,performing estimations and hypothesis tests, determining relationships among variables and making predictions. It uses probability i,e., the chance of event occuring 9/6/2015 CHS deptt 7 The origin of descriptive Statistics can be traced to data collection methods used in censuses taken by the Babylonians and Egyptians between 4500 and 3000 B.C. In addition the Roman Emperor Augustus (27 B.C-A.D. 17) conducted surveys on births and deaths of the citizens of the empire, as well as the number of livestock each owned and the crops each citizen harvested yearly. 9/6/2015 CHS deptt 8 Inferential Statistics originated in the 1600s, when John Graunt published his book on population growth , Natural and Political Observations Made upon the Bills of Mortality. About the same time ,another mathematician/astronomer , Edmund Hally, published the first complete mortality tables.( insurance companies use mortality tables to determine life insurance rates). 9/6/2015 CHS deptt 9 Application of Statistical methods to the solution of biological problems 9/6/2015 CHS deptt 10 In Epidemiology In demography Morbidity and mortality rates and ratios. Collection and registration of vital events.(Births ,Deaths , Marriages and divorces) Sampling for different statistical procedures. To know the frequency of different diseases and biological problems. For interpretation of data. To know about association and causation of diseases. 9/6/2015 CHS deptt 11 9/6/2015 CHS deptt 12 Record of observations Facts and figures Any piece of information Information When data is processed and made meaningful 9/6/2015 CHS deptt 13 Data are numbers which can be measured or can be obtained by counting. Biostatistics is concerned with the interpretation of the data and the communication of information about the data. 9/6/2015 CHS deptt 14 Data are obtained from Analysis of records Surveys Counting Experiments Reports 9/6/2015 CHS deptt 15 A characteristics ,object and property that assumes different numerical value for each possible outcome/individual/element of the population or sample is called a variable. The actual property measured on the individual selected for sample. E.g. Height ,weight ,temprature,age,smoking, 9/6/2015 CHS deptt 16 A random variable is one that cannot be predicted in advance because it arises by chance. Observations or measurements are used to obtain the value of a random variable. Random variables may be discrete or continuous. Discrete random variable A discrete random variable has gaps or interruptions in the values that it can have. The values may be whole numbers or have spaces between them. Continuous random variable A continuous random variable does not have gaps in the values it can assume. Its properties are like the real numbers. 9/6/2015 CHS deptt 17 9/6/2015 CHS deptt 18 9/6/2015 CHS deptt 19 Independent and dependent Independent variables are presumed causes and dependent variables are presumed effects. 9/6/2015 CHS deptt 20 9/6/2015 CHS deptt 21 The whole set of things about which we want to know. In biostatistics population can be human beings , ECG machines , Paracetamol tablets. A population is the collection or set of all of the values that a variable may have. A sample is a part of a population. 9/6/2015 CHS deptt 22 A part or subset of population for actual study. OR A collection of individual observations selected by a specific procedure from a population. 9/6/2015 CHS deptt 23 Measurement variable Continuous variables Discontinuous variables or discrete variable Ranked variables Categorical variable 9/6/2015 CHS deptt 24 Continuous variables Which at least theoretically can assume an infinite number of values between any two points . e. g length ,period of time ,height , weight , age , Discrete, Discontinuous variables That has only certain fixed numerical values with no intermediate values possible in between. e.g. number of offsprings , no. of teeth, no. of glands. 9/6/2015 CHS deptt 25 Which cannot be measured but ranked or ordered .e.g. rank order of pupa emergence or seed germination. 9/6/2015 CHS deptt 26 The characteristics that are qualitative in character and hence cannot be expressed numerically( or quantitatively) are called descriptive characteristics or attributes. The sex of a newly born baby. Eye color of a girl. The language of a Arabian visitor. The style of a speaker 9/6/2015 CHS deptt 27 Data consists of variables. There are four scales of measurement Nominal(category) Ordinal(category) Interval(quantity ,continuous ) Ratio(quantity , continuous) 9/6/2015 CHS deptt 28 Scale Characteristic question Example Nominal Is A different than B? Marital status Eye color Gender Religious affiliations Race ordinal Is A bigger than B? Stage of disease Severity of pain Level of satisfaction Interval By how many units do A and B differs? Temperature SAT score Ratio How many times bigger than B is A? Distance Length Time until death Weight 9/6/2015 CHS deptt 29 Classifies persons or things based on the characteristic being assessed No information is given on quantity or amount A variable without an intrinsic order. Examples Male or female Nationality (American , Mexican , Pakistani) Favorite pet( dog , cat, fish, snake) 9/6/2015 CHS deptt 30 Classifies persons or things based on the characteristic being assessed Can be placed in meaningful order, Indicates “more than” or “less than” Does not indicate how much more or how much less than Example: Rating a student’s performance as ‘good’, ‘fair’, ‘poor’ 9/6/2015 CHS deptt 31 Classifies persons or things based on the characteristic being assessed Indicates “more than” or “less than ” and the magnitude of the observation There is no true zero or meaningful zero. Examples Temperature Year of birth Date of diagnosis 9/6/2015 CHS deptt 32 Classifies persons or things based on the characteristic being assessed Indicates “more than” or “less than” and the magnitude of the observation Zero point is indicated True ratios exist when the same variable is measured on the different members f the population. Examples: Height Weight Age 9/6/2015 CHS deptt 33 Date of diagnosis Town of residence Age (years) Sex 9/6/2015 CHS deptt 34 Date of diagnosis: Interval Town of residence: Nominal Age (years): Ratio Sex : Nominal 9/6/2015 CHS deptt 35 Name the scale of measurement for each variable below: Year of birth: Marital status of a women: Identification number of study participants: Class rank: Length of infants at ANC clinic: 9/6/2015 CHS deptt 36 Year of birth: Interval Marital status of a women: Nominal Identification number : Nominal Class rank: Ordinal Length/Height of infants at ANC clinic: Ratio 9/6/2015 CHS deptt 37 Identify whether the following data is discrete or continuous Distance from primary health center to reference lab: Number of times a child under 5 has experienced fever in the last month: Number of fatal accidents on a road over the past year: Weight gained or lost by a 9 month old in the past 3 months: 9/6/2015 CHS deptt 38 Distance from primary health center to reference lab: Continuous Number of times a child under 5 has experienced fever in the last month: Discrete Number of fatal accidents on a road over the past year: Discrete Weight gained or lost by a 9 month old in the past 3 months: Continuous 9/6/2015 CHS deptt 39 9/6/2015 CHS deptt 40