BIOSTATISTIC FOR DENTISTS PART 3.pptx

BIOSTATISTICS

1. BIOSTATISTICS PART 1 DR PRANAV KULKARNI Dept of Periodontology

2. CONTENTS DEFINITION COMMON STATISTICAL TERMS DATA TYPES OF DATA PRESENTATION OF DATA MEASURES OF CENTRAL TENDANCY USES OF DATA USES OF STATISTICS

3. Statistic or datum means a measured or counted fact or piece of information stated as a figure such as height of one person , birth of a baby ,etc.

4. It can be defined as an art and science of collection , compilation, presentation, analysis and logical interpretation of biological data affected by multiplicity of factors. It is the term used when the tools of statistics are applied to data that is derived from biological sciences such as medicine or dentistry. DEFINITION

5. COMMON STATISTICAL TERMS Variable:- A characteristic that takes on different values in different persons ,place or things . It is denoted by X and notation for orderly series as X 1 , X 2 ,X 3 ….. X n Constant:- A character that do not vary. e.g mean , standard deviation etc

6. Observation:- An event and its measurement. e.g. blood pressure . Observational unit:- The source that gives observations such as object, person etc. Data :- a set of values recorded on one or more observational units.

7. Population:- It is an entire group of people or study elements – person ,things or measurements for which we have an interest at a particular time .it may be finite or infinite. Sample :- It is defined as a part of the population Sampling unit:- each member of the population

8. Parameter:- it is the summary value or constant of the variable that describes the population such as mean variance , correlation coefficient ,proportion ,etc. e.g. mean height ,birth rate

9. Parametric test:- one in which population constants are used such as mean , variance etc and data tend to follow one assumed or established distribution such as normal, binomial ,Poisson, etc Non- parametric tests:- no constants are used ,data do not follow any specific distribution and no assumptions are made . E.g. to classify good, better and best you allocate arbitrary no. to each category.

10. DATA Data analysis is a cornerstone in reporting research findings. Data are set of values of one or more variables recorded on one or more individuals. Data consists of distinct observations of attributes or events that carry little meaning when considered alone. Data needs to be transformed into information by reducing, summarizing and adjusting them for variations in the age and sex composition of the population so that comparisons over time and place are possible.

11. Types of data Qualitative / Enumeration data Quantitative / measurement data Discrete Data Continuous Data Grouped Data Ungrouped Data

12. Primary data Secondary data Nominal data Ordinal data

13. TYPES OF DATA

14. PRIMARY DATA It is the data obtained by the investigator himself. This is the first hand information . ADVANTAGES Precise information. Reliable DISADVANTAGES Time consuming Expensive

15. Secondary data The data already recorded is utilized to serve the purpose of the objective of the study. eg : the records of the OPD of dental clinics. METHOD OF COLLECTION OF DATA Questionnaires Surveys Records Interviews

16. Quantitative DATA There is a natural numeric s c ale (numerical value) C an be subdivided into Interval and Ratio data. E.g. age , height, weigh t etc. Interval – Placed in intervals or order - Uses a scale graded in equal increments - Height, weight, blood pressure Ratio – Interval scale data is placed with meaningful ratio - Biomedically most significant - Presented in frequency distribution

17. Nominal – Qualitative data Male / Female White / Black Socio- economic status Ordinal – Arranged in rank / order Ramu is taller than Ravi and Ravi is taller than Ajay Qualitative DATA Measuring a characteristic for which there is no natural numeric scale. C an be subdivided into Nominal and Ordinal data. Eg gender, color etc.

18. PRESENTATION OF DATA The variables distributed in a population or a sample can be of interest for various reasons. Statistical data once collected must be arranged purposively in order to bring out most important points clearly and strikingly. Therefore the manner in which statistical data is presented is of utmost importance.

19. Principles of data presentation:- The data should be :- arranged in such a way that it will arouse interest in reader. Made sufficiently concise without loosing important details.

20. Presented in simple form to enable the reader to form quick impression and to draw some conclusions directly or indirectly. Facilitate further statistical analysis. Able to define a problem and suggest its solution.

21. TABULATION Tables are simple devices used for presentation of statistical data. Tabulation is the first step before data is used for analysis or interpretation.

22. There are general principles that should be borne in mind before designing tables Tables should be as simple as possible. 2 or 3 small tables are preferred to a single large table containing many details or variables. The headings of columns and rows should be clear and concise. The data must be presented according to size or importance chronologically, alphabetically or geographically If percentage or average are compared they should be placed as close as possible. The specific units of measure for the data should be given. Tables should be self-explanatory. Codes, abbreviations or symbols should be explained in detail in a footnote.

23. eg . Students in a primary school CLASSES NUMBER OF STUDENTS I 68 II 65 III 63 IV 60 SIMPLE TABLE

24. MASTER TABLE SR. NO AGE SEX EDUCATION D M F DMF PI 001 002 003 These are the tables which contain all the data obtained from a survey

25. FREQUENCY DISTRIBUTION TABLE In frequency distribution table the data is first split up into convenient groups (class intervals) and the number of items (frequency) occur in each group. The data shown is also known as raw data.

26. CHARTS AND DIAGRAMS They are useful methods of presenting simple statistical data. They have a powerful impact on the imagination of people therefore there are a popular media of expressing statistical data. ADVANTAGES Diagrams are better retained in the memory than statistical tables. If the diagram are drawn simple the impact on the reader is much higher. DISADVANTAGES Lots of details of the original data may be lost in charts and diagrams.

27. BAR CHARTS It is a way of presenting a set of numbers by the length of a bar. Simple bar chart

28. Component bar chart: This diagram is used to compare the sub-groups between different major groups of observation. This contrasting information can also be shown using multiple bars.

29. PIE CHART It represents the total frequency. It is divided into different sectors corresponding to the frequencies of the variables in the distribution.

30. LINE GRAPH When the quantity is a continuous variable ie time, temperature. Data is plotted as a continuous line.

31. HISTOGRAMS It is a pictorial diagram of frequency distribution, eg : age-wise prevalence of dental caries. PICTOGRAMS Small pictures or symbols are used for presenting data. They are specially used for the common man.

32. MEASURES OF CENTRAL TENDENCY Main objective- is to condense the entire mass of data and to facilitate comparison. The most common measures of central tendency that are used in dental sciences are- Arithmetic mean Median Mode

33. MEAN It is obtained by adding the individual observations and dividing the total by number of observations. Eg the following gives you the fasting blood glucose levels of a sample of 10 children. 2 3 4 5 6 7 8 9 10 62 63 65 65 65 65 68 70 71 Total = 650 Mean= 650/10 Mean is denoted by the sign (X bar)

34. ADVANTAGES: Easy to calculate Easily understood Utilizes entire data Affords good comparison DISADVANTAGES: Mean is affected by extreme values. In such cases it leads to bad interpretation.

35. MEDIAN In median the data are arranged in an ascending or descending order of magnitude and the value of middle observation is located. Eg Diastolic blood pressure of 10 individuals 1 2 3 4 5 6 7 8 9 10 75 81 79 71 95 75 77 84 90 Arrange them in ascending or descending order 71,75,75,77,79,81,83,84,90,95 Median = 79+81 ̷ 2= 80 If there are only 9 observations then median = 79

36. Advantages It is more representative than mean. It does not depend on every observations. It is not affected by extreme values. What is extreme value? If suppose the income of 7 people is as follows 1 2 3 4 5 6 7 5 5 5 7 10 20 102 Mean 154/7= 22 Median = 7 Here the mean is affected because of extreme value (102)

37. MODE Mode is that value which occurs with the greatest frequency. A distribution may have more than one mode. Eg : Diastolic blood pressure of 10 individuals. 85, 75,81,79,71,80,75,78,72,73 Here mode= 75 ie distribution is unimode 85,75,81,79,80,71,80,78,75,73 Here mode = 75 & 80 ie distribution is bimode

38. ADVANTAGES: It eliminates extreme variation. Easily located by mean inspection. Easy to understand. DISADVANTAGES: Exact location is uncertain. In small number of cases there may be no mode at all because no values may be repeated, therefore it is not used in medical or biologic statistics. When mode is ill-defined, it can be calculated using the relation Mode = 3 Median – 2 Mean

39. USES OF DATA In designing a health care programme . In evaluating the effectiveness of an on going program. In determining the needs of a specific population. In evaluating the scientific accuracy of a journal article.

40. USES OF STATISTICS To measure the state of health of community and to identify its health problems, their nature etc. For comparing health status of one country with that of another and for comparing the present status with that of the past. For planning and administration of dental health services. For prediction of health trends. To evaluate progress and development of disease .

41. THANK YOU!!