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COMMUNITY DENTAL HEALTH

COMMUNITY DENTAL HEALTH. STATISTICS. Statistics is the field of study which concerns itself with the art and science of data analysis: Planning, collecting, organizing, analyzing, interpreting, summarizing and presenting the data

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COMMUNITY DENTAL HEALTH

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  1. COMMUNITY DENTAL HEALTH Algonquin College - Janet Ladas

  2. STATISTICS Statistics is the field of study which concerns itself with the art and science of data analysis: • Planning, collecting, organizing, analyzing, interpreting, summarizing and presenting the data Statistics, when used in the plural form, refers to the specific bits of data which either have been or are about to be gathered. Algonquin College - Janet Ladas

  3. STATISTICS Foreign Language: • Special meaning for words like mean, regression, normal, confidence, correlation, population, discrete, conditional, union, posterior, hypothesis etc., etc., etc. Logic related to statistics more than math. (H.S. Algebra) – computers * Complex and demanding subject area Algonquin College - Janet Ladas

  4. INTRODUCTION TO BIOSTATISTICS Biostatistics: The mathematics of collection, organization and interpretation of numeric data having to do with living organisms. Techniques to manage data: • Descriptive • Inferential Algonquin College - Janet Ladas

  5. INTRODUCTION TO BIOSTATISTICS Uses for data: (To name a few) • Designing a health care program or facility • Evaluating the effectiveness of an ongoing program • Determining needs of a specific population • Evaluating the accuracy of a journal article Algonquin College - Janet Ladas

  6. EPIDEMIOLOGY The scientific study of factors that influence the frequency and distribution of disease in a population. Algonquin College - Janet Ladas

  7. METHODS OF MEASURING ORAL DISEASE Counts: • A simple number of cases of occurrence • Useful when there is a low prevalence e.g. 12 cases of oral cancer Proportions: • A count can be turned into a proportion by adding a denominator thus determining prevalence e.g. 12 cases in a population of 1,500 students • Does not include a time dimension thus includes new cases as well as longstanding ones Algonquin College - Janet Ladas

  8. METHODS OF MEASURING ORAL DISEASE Rates: • A proportion that uses a standardized denominator and includes a time dimension Types of Rates: (As applied to Biostatistics) Morbidity Rate: • The proportion of people ill with the disease over a specified time span formula: # of new cases /100,000 people / year e.g.: 12 / 1,500 / 2000 Algonquin College - Janet Ladas

  9. METHODS OF MEASURING ORAL DISEASE Mortality Rate: • The proportion of people who die from the disease during a period of time formula: # of deaths / 100,000 people / year e.g.: 8 / 1,500 / 2000 Case Rate: • Frequency of occurrence of the condition / disease formula: # of occurrences / # of births / year e.g.: 1 / 700 / 2001 (Cleft Palatte Cases) n.b. rates can be converted into percentages Algonquin College - Janet Ladas

  10. INDEXES (INDICES) An index is a measure of quantification of epidemiological data • A numerical value on a graduated scale • Scores correspond to specific criteria • Have definite upper and lower limits Examples: • DMFT’s – caries activity – best known – irreversible • RCI – root caries - irreversible Algonquin College - Janet Ladas

  11. INDEXES (INDICES) • GBI – Gingival Bleeding – reversible • CPITN – Community Periodontal Index of Treatment Needs • DFI – Dental Fluorosis Note: • No generic, all purpose scale • Depends on the reason for using that measure, how to handle it reliably and what you want to demonstrate Algonquin College - Janet Ladas

  12. DENTAL HEALTH INDICES Dental conditions readily lend themselves to study because we have specific tools for speed and accuracy of measurement. Index Properties • Clear, simple, objective • Valid – measures what it is supposed to • Reliable – consistent on repetition • Quantifiable – data can be analyzed • Sensitive – can detect small shifts in either direction • Acceptable – not painful or demeaning to the subject • Clinically significant and meaningful Algonquin College - Janet Ladas

  13. CARIES ACTIVITIES INDICES DMFT : decayed, missing, filled permanent teeth deft : primary teeth • Each tooth must have a score but only one (DMF or sound) • Recurrent caries = decayed (D) • Missing teeth = extracted or due to be extracted due to caries • Teeth not deemed as missing = unerupted, congenitally absent, accidentally lost or extracted for ortho. Purpose • Third molars not scored DMFT and deft scores are objective thus require high agreement between examiners. DMFS and defs (surfaces) are more subjective thus less reliable. Algonquin College - Janet Ladas

  14. FACTS ABOUT DATA Two types of data: Qualitative: labels used to identify an item when it cannot be numerically identified. e.g.: marital status, car colour, occupation (attributes) n.b.: has absolutely nothing to do with the quality of the data Quantitative: characteristics that can be expressed numerically. Any mathematical manipulation that is carried out on them will have meaning. e.g.: height, length, volume, number of DMFT’s (variates) Algonquin College - Janet Ladas

  15. FACTS ABOUT DATA Data Set: • Relates to a given group of data • Generally denoted with brackets e.g.: Q = {17, 15, 18, 13, 12} Data Point: • A single observation in a data set e.g.: 15 is the second data point in the above data set Data is Plural: • Datum is singular Algonquin College - Janet Ladas

  16. FACTS ABOUT DATA Raw Data: • Data still in the form that it was when originally gathered. e.g.: A = {14, 11, 17, 9, 12} Rank Ordering: • Rearranging data in order – usually ascending e.g.: A = {9, 11, 12, 14, 17} Algonquin College - Janet Ladas

  17. DATA MANAGEMENT Grouping data to make it easier to understand. Descriptive Technique: • Used to describe and summarize a set of numerical data • Tabular and graphical methods • Apply to generalizations made about the group studied Algonquin College - Janet Ladas

  18. DESCRIPTIVE DATA DISPLAY TYPES An Array: A group of scores arranged from lowest to highest in value. e.g.: Histology test results – 24 students: = Raw Data Array: 19, 25, 26, 28, 30, 30, 31, 33, 33, 35, 36, 38, 38, 38, 39, 40, 41, 41, 41, 42, 44, 44, 46, 49 / 50 total Algonquin College - Janet Ladas

  19. DESCRIPTIVE DATA DISPLAY TYPES Arrays are bulky and hard to read, thus an alternative is: Frequency Distribution: • An organization of scores from lowest to highest which includes the number of times each score value occurs in the data set. Algonquin College - Janet Ladas

  20. DESCRIPTIVE DATA DISPLAY TYPES Frequency Distribution – 3 Types: • Ungrouped • Each possible score value of the variable being measured is represented in the display and the frequency of occurrence of the value is recorded. Sample: Algonquin College - Janet Ladas

  21. DESCRIPTIVE DATA DISPLAY TYPES Frequency Distribution – Ungrouped: Algonquin College - Janet Ladas

  22. DESCRIPTIVE DATA DISPLAY TYPES 2. Grouped Frequency Distribution: When a broad range of values on the measurement is possible (i.e. > 30), the range is collapsed by grouping scores together into smaller value ranges. Algonquin College - Janet Ladas

  23. DESCRIPTIVE DATA DISPLAY TYPES 3. Cumulative Frequency Distribution: Used with score groupings where the frequency of any one group includes all instances of scores in that group plus all the groups of lower score values. Algonquin College - Janet Ladas

  24. GRAPHS AND TABLES • Histograms • Polygons – most frequently used • Bar graphs • Pie charts Algonquin College - Janet Ladas

  25. PRINCIPLES FOR CONSTRUCTING GRAPHS AND TABLES (Course supplement Pages 6, 7, 8) • Items in separate columns should be clearly defined and the units of measure of the observation included • A suitable descriptive title should define the contents as a whole • Rate statistics clearly stated (per 100 or per 1,000) • When possible and practical, frequency distribution should be in full Algonquin College - Janet Ladas

  26. PRINCIPLES FOR CONSTRUCTING GRAPHS AND TABLES 5. When using rates or proportions, include numbers of observations 6. Clearly state when using percentage 7. Do not include too much on the same table 8. If observations are excluded, give reason and criteria Algonquin College - Janet Ladas

  27. GRAPHING TECHNIQUES • Descriptive data in pictorial fashion as a graph Y Axis (Ordinate) = vertical axis • Represents frequency of occurrence • Represents score value X Axis (Abscissa) = horizontal axis • Represents scale of measurement of the characteristic of the sample • Indicates the variable or group studied Algonquin College - Janet Ladas

  28. FREQUENCY HISTOGRAM See course supplement page 8. • A histogram is a graphical method for variate (quantitative characteristic) data. Note that there is no space between the vertical bars. Algonquin College - Janet Ladas

  29. FREQUENCY POLYGON See course supplement page 9. • A line graph created by joining the frequency / scale value coordinate points for each value in the scale represented. Used for variate data. Algonquin College - Janet Ladas

  30. BAR GRAPH See course supplement page 10. 2-dimensional pictorial display of attribute data that are discrete in nature • Bars do not touch Algonquin College - Janet Ladas

  31. CENTRAL TENDENCY Term in statistics that describes where the data set is located. Measures of Central Tendency Used to describe what is typical in the sample group based on the data gathered. Three Main Indicators: • Mean - Median - Mode Algonquin College - Janet Ladas

  32. CENTRAL TENDENCY Mean = arithmetic average of scores • Mean symbol is ( x ) • Scores are all added then divided by the number of scores. • The most common measure: Data set {3, 7, 9, 4, 9, 16} = 48 / 6 = 8 Algonquin College - Janet Ladas

  33. CENTRAL TENDENCY Median: Is the point that divides the distribution of scores into 2 equal parts – 50 / 50 • With odd set of numbers, median is the datum in the middle: i.e.: {3, 7, 2, 5, 9} rearranged to {2, 3, 5, 7, 9} median = 5 • With even set of numbers, median is the average of the two middle values: i.e.: {4, 7, 1, 3, 8, 2} rearranged to {1, 2, 3, 4, 7, 8} 3 + 4 = 7 / 2 median = 3.5 Algonquin College - Janet Ladas

  34. CENTRAL TENDENCY Mode: Is the most frequently occurring score in a distribution: i.e.: {4, 3, 4, 9, 7, 2} mode = 4 i.e.: {3, 8, 4, 2, 4, 9, 7, 4, 9, 1, 9} bimodal data set 4 and 9 Algonquin College - Janet Ladas

  35. QUESTIONS Determine the mode, mean and median for: • Survival time, in months, for 10 patients following a new cancer treatment: 24, 8, 12, 3, 20, 18, 24, 19, 27, 25 • Salaries of 7 dental hygienists and 2 dentists in a productive office: 88,500 36,500 28,300 80,000 34,000 28,300 41,000 32,000 28,300 Algonquin College - Janet Ladas

  36. “If a statistician had her hair on fire and her feet in a block of ice, she would say that “on the average, she felt good.”” What is she referring to? What is she ignoring? Algonquin College - Janet Ladas

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