I. Chap1 Introduction to Biostatistics .pptx

This is introduction may enable the readers to have information about Biostatistics

1. Oda Bultum University College of Health science BIOSTATISTICS for Midwifery students (2 nd yr .) By: Eyasu B. (BSc PH, MPH) [email protected] March ,2024 G.C 3/8/2024 Biostatistics for Health Science students 1

2. CHAPTER ONE Introduction to Biostatistics Learning objectives After completing this chapter, the student will be able to: Define s tatistics and Biostatistics Enumerate the importance and limitations of statistics Identify rational of Biostatic in health sciences Identify types scale of measurement Define data and variables Type od data and type of variables 3/8/2024 2

3. What is statistics? Statistics is a numerical representation of things. is a field of study that deals with Collecting data Presenting data summarizing data Drawing inferences (analyzing &interpreting ) of numerical Data for understanding a phenomenon or making wise decisions. 3/8/2024 3

4. What is Biostatistics? It is the application of statistical methods to the biological and life sciences. Rationale of Biostatistics Provides methods of organizing information Assessment of health status Resource allocation (planning ) More and more things are now measured quantitatively in medicine and public health. 3/8/2024 4

5. Rationale of Biostatistics….. Evaluation of new vaccine or drug How effective is the vaccine (drug )? Is the effect due to chance or some bias ? Drawing of inferences Information from sample to population Essential for understanding appraisal and critique of scientific literature. 5 3/8/2024

6. Characteristics of statistical data They must be in aggregates: A single fact, even though numerically stated, cannot be called statistics . They must be affected by a multiplicity of causes. They must have been collected in a systematic manner for a predetermined purpose. They must be comparable either in point of time, space or condition .

7. Limitations of statistics As a science, statistics has its own limitation Deals with only quantitative information. Deals with aggregate of facts, not with individual. Data are approximately , not mathematical correct 3/8/2024 7

8. Types of Biostatistics Descriptive Biostatistics: Describing the characteristics of sample. Ways of organizing and summarizing data  – Includes   Collection   Organization   Summarization   Presentation of data 3/8/2024 8

9. cont.…. Descriptive biostatistics include:   Tables Graphs (Bar chart, Pie chart, Histogram, Scatter plot, etc.)       Numerical summary measures  Measures of central tendency (location)  Measures of variability (dispersion) 3/8/2024 9

10. cont.… 2. Inferential statistics: D eals with techniques of making conclusions about the population based on the information obtained from a sample drawn from that population. Inferential statistics builds upon descriptive statistics. Includes:  -Estimation -hypothesis  testing,  -making predictions/association etc . 3/8/2024 10

11. Cont.… 11

12. Data A re numbers which can be obtained from taking measurements or can be obtained by counting or observation Numerical descriptions  of things  The  raw material  for statistics. Divided in to Primary data: collected from the items or individual respondents directly. Secondary data: a data which had been collected by certain people or organization, & the information is used for other purpose by other people. E.g. - CSA: Central statistics agency 3/8/2024 12

13. Sources of data Routine health facility data   – Hospital, health center, clinic, health post  Routinely kept records, reports  Literature (published and unpublished)  Disease notifications, Epidemic reports  Census, Civil or vital registration  Laboratories Surveys  etc.  3/8/2024 13

14. Population and sample Population: refers to any well defined groups of subjects/objects who share common characteristics.    Sample : A  small  group  or  subset  of  a  population  about  which information is  actually  obtained Samples  are  used  to  describe & make inferences  about  the  populations  from  which  they arise  Statistical methods are based on these samples  Samples  should  be  selected  using  a  suitable method so that it can be representative (random sample) 3/8/2024 14

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16. Variable Variable : A characteristic which takes different values in different persons, places, or things . Any aspect of an individual or object that is measured (e.g. BP) or recorded (e.g. age, sex) and takes any value. There may be one variable in a study or many. E.g. A study of treatment outcome of TB sex, weight (kg), smear result (Positive, negative or uncertain), culture result (negative, positive), cured after 6 months (yes/no ). 3/8/2024 16

17. Variables can be broadly classified into: Categorical (or Qualitative ) and Numerical variables(or Quantitative). 3/8/2024 17

18. Categorical variables : A variable which can not be measured in quantitative form but can only be sorted by name or categories. Not able to be measured as we measure height or weight. Classified in to two Nominal Ordinal 3/8/2024 18

19. A. Nominal : The simplest type of variable, in which the values fall into un-ordered categories or classes Uses names, labels or symbols to assign each measurement. Examples: Blood group 1. A 2.B, 3 AB, 4. O Sex - 1. male 2. female 3/8/2024 19 Here the number have no meaning rather than labeling!

20. B. Ordinal : Assigns each measurement to one of a limited number of categories that are ranked in terms of order. Although non-numerical , can be considered to have a natural ordering Examples: Breast cancer stages 1 st stage, 2 nd stage , 3 rd stage, 4 th stage 3/8/2024 20 Here the number have meaning i.e. 4> 3>2>1 in severity

21. 2. Quantitative variables A variable that can be measured or counted and expressed numerically . E.g Height, weight, # of children, etc. Has the notion of magnitude . Classified in to two Discrete Continuous variable : 3/8/2024 21

22. A. Discrete It can only have a limited number of discrete values (usually whole numbers ). E.g. the number of episodes of diarrhoea a child has had in a year. You can’t have 12.5 episodes of diarrhoea Characterized by gaps or interruptions in the values. Both the order and magnitude of the values matter. The values are not just labels, but are actual measurable quantities. 3/8/2024 22

23. B. Continuous variable : It can have an infinite number of possible values in any given interval. Both the magnitude and the order of the values matter. Does not possess the gaps or interruptions E.g. Weight, Height, etc. 3/8/2024 23

24. Variables Qualitative ( categorical) Quantitative (numerical) Nominal e.g. ethnic group Ordinal e.g. response to treatment Discrete e.g. # of admissions Continuous e.g. height Types of variables Measurement scales SUMMARY 3/8/2024 24

25. Scales of measurement All measurements are not the same. Measuring weight = eg. 40kg Measuring the status of a patient on scale = “improved”, “stable”, “not improved”. There are four types of scales of measurement. Nominal Ordinal Interval Ratio scale 3/8/2024 25

26. 1.Nominal scale : The simplest type of scale of measurement, in which the values fall into un-ordered categories or classes Uses names, labels or symbols to assign each measurement. Example : Race/Ethnicity: 1. Black 2. White 3. Latino 4. Other 3/8/2024 26

27. If nominal data take only two possible values, they are called dichotomous or binary . E.g. sex is dichotomous (male or female). Yes/no questions E.g., cured from TB at 6 months of Rx 3/8/2024 27

28. 2. Ordinal scale : Assigns each measurement to one of a limited number of categories that are ranked in terms of order. Although non-numerical , can be considered to have a natural ordering Examples: Patient status, cancer stages 3/8/2024 28

29. Example of ordinal scale: Pain level: 1. None 2. Mild 3. Moderate 4. Severe The numbers have LIMITED meaning 4>3>2>1 is all we know apart from their utility as labels 3/8/2024 29

30. 3 . Interval scale : Measured on a continuum and differences between any two numbers on a scale are of known size. Example: Temp. in o F on 4 consecutive days Days: A B C D Temp. o F: 50 55 60 65 For these data, not only is day A with 50 o F cooler than day D with 65 o but is 15 o cooler. It has no true zero point . “0” is arbitrarily chosen and doesn’t reflect the absence the attribute. 3/8/2024 30

31. 4. Ratio scale : It is the highest scale of measurement. Measurement begins at a true zero point and the scale has equal space. Examples: Height, weight, BP, etc.   N.B measurement   on  a  higher  scale  can  be transformed into one on a lower scale, but not vice versa . E.g. W.t of a child= 3000gm, (ratio scale) w.t of a child= under weight, normal, over weight ( Ordinal scale ) 3/8/2024 31

32. Nominal Ordinal Interval Ratio Degree of precision in measuring 3/8/2024 32

33. Dependent  vs. Independent  Variable   Dependent :   The   variable  (s)  we  measure  as  the   outcome   of  interest , or  response.   Independent :  The  variable  that  explains   the  dependent   variable  (s),  or  explanatory/ predictor v ariable. Eg. If any want to study the magnitude of Anemia and associated factors among pregnant women in chiro town. What is the dependent variable? List the independent variables? 3/8/2024 33

34. Quiz1 (5%) Q1 1.Classify the below variables as quantitative and qualitative and write in bracket as nominal, ordinal, discrete or continuous Number of female students in your class Marital status: 1=married, 2=single, 3=widowed, 4=divorced Prognosis: 1=very good, 2=good, 3=fair, 4=bad, 5=very bad First temperature following admission ( F⁰) Received Po medications: 1=yes, 2= no Weight of infant at birth (gm) Type of disease: 1= chronic 2= acute 3/8/2024 34

35. Q 2 35 2. Suppose a researcher studied the causes of lung cancer. He collected data on smoking status(Yes/No), age, sex, alcohol intake ( Yes/No) and history of exposure to radiation(Yes/No) of the study participants . What are variables included in this research ? Which one is dependent variable and why ? Which scale of measurement does the dependent variable ? List the independent variables?