Introduction to biostatistics
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The document discusses the importance of descriptive statistics in public health, particularly in infection prevention and control. It covers the various types of data, measurement scales, and methods for organizing and summarizing data, including the use of frequency tables, graphs, and measures of central tendency. Additionally, it explores different types of variables, their categorization, and the application of statistical concepts in healthcare settings.
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June 22, 2013 Dr Fayssal Farahat, MD 37
Arithmetic Mean
ExtremesHR
variation
1
2
3
4
5
6
7
8
9
10
19.2
51.9
33.1
86.7
29.1
45.3
16.4
85.7
18.9
42.6
42.9
32.1
Consider each variable
X
June 22, 2013 Dr Fayssal Farahat, MD 38
Weighted Mean
Interval Frequency Valid % Cumulative %
2-20
21-30
31-40
41-50
51-60
61-70
71-80
81-90
>90
Total
46
70
108
106
74
72
42
29
33
580
7.9
12.1
18.6
18.3
12.8
12.4
7.2
5.0
5.7
100.0
7.9
20.0
38.6
56.9
69.7
82.1
89.3
94.3
100
[(11 x 46) + (25 x 70) + ….+ (85 x 29) + (100 x 33)] / 580 = 49.1
X
?
June 22, 2013 Dr Fayssal Farahat, MD 39
Median
Middle observation
Odd Even
Extremes
Consider each variable
Ordinal data](https://image.slidesharecdn.com/introductiontobiostatisticsi-220613-130622082221-phpapp02/85/Introduction-to-biostatistics-13-320.jpg)
Introduction to biostatistics
- 1. 1 June 22, 2013 Dr Fayssal Farahat, MD 1 Dr. Fayssal M Farahat, MBBCh, MSc, PhD Consultant Public Health Infection Prevention and Control King AbdulAziz Medical City–Jeddah National Guard Health Affairs Descriptive Statistics June 22, 2013 Dr Fayssal Farahat, MD 2 “Whatever you can not measure, you can not manage” June 22, 2013 Dr Fayssal Farahat, MD 3 Statistics business education psychology Biology and Medicine Biostatistics
- 2. 2 June 22, 2013 Dr Fayssal Farahat, MD 4 Statistics Collection Presentation Analysis Draw inferences June 22, 2013 Dr Fayssal Farahat, MD 5 Data = numbers Measurement Counting A nurse takes a patient’s temperature A hospital administrator counts number of discharged patients on a given day. June 22, 2013 Dr Fayssal Farahat, MD 6 Data Data Data Data Decision The procedure by which we reach a conclusion about a population on the basis of information contained in a sample drawn from this population
- 3. 3 June 22, 2013 Dr Fayssal Farahat, MD 7 Students’ scores: 75, 95, 60, 93, 85, 84, 76, 92, 62, 83, 80, 90, 64, 75,79, 32, 78, 64, 98, 73,88, 61, 82, 86, 79, 78, 80, 55 How useful would that list of number be to you? How to get information out of data … FIRST STEP, the data have to be organized and Summarized. Data INFO June 22, 2013 Dr Fayssal Farahat, MD 8 Sources of Data Primary Data Collection & Analysis Secondary Data Collection & Analysis Client satisfaction & Identification Surveys Lifestyle and health behavior surveys Focus Group discussions Hospital Records inpatients outpatients Birth Death External sources (published reports) June 22, 2013 Dr Fayssal Farahat, MD 9 Measurement
- 4. 4 June 22, 2013 Dr Fayssal Farahat, MD 10 Variable = Characteristicnot the same when observed in different possessors. June 22, 2013 Dr Fayssal Farahat, MD 11 VARIABLES June 22, 2013 Dr Fayssal Farahat, MD 12 Quantitative Discrete منفصلة No fractions عشرية كسور ال Continuous متصلة Fractions عشرية كسور
- 5. 5 June 22, 2013 Dr Fayssal Farahat, MD 13 Qualitative Ordinal ترتيبية Nominal اسمية June 22, 2013 Dr Fayssal Farahat, MD 14 Discrete منفصلة • Number of pregnancies • Number of children • Family size • Heart rate • Respiratory rate • Number of cigarettes June 22, 2013 Dr Fayssal Farahat, MD 15 Continuous متصلة • WEIGHT • HIGHT • AGE • TEPERATURE • BLOOD PRESSURE • RBS • AMOUNT OF URINE • BODY SURFACE AREA
- 6. 6 June 22, 2013 Dr Fayssal Farahat, MD 16 Nominal - Gender :" Male – female. " - Marital status: married, single, widow, divorced (1) (2) (1) (2) (3) (4) June 22, 2013 Dr Fayssal Farahat, MD 17 Ordinal - grade :" A+ A B+ B C+ C D+ D " . - Educational level: 1ry, 2ry, university - Income: < 5000, 5000-10.000, >10.000 (1) (2) (3) (4) (5) (6) (7) (1) (2) (3) (1) (2) (3) June 22, 2013 Dr Fayssal Farahat, MD 18 Quantitative Qualitative High systole Qualitative x Quantitative 200 x
- 7. 7 June 22, 2013 Dr Fayssal Farahat, MD 19 Measurement Scales Nominal Ordinal Interval Ratio June 22, 2013 Dr Fayssal Farahat, MD 20 Temperature True zero Weight June 22, 2013 Dr Fayssal Farahat, MD 21 The distinction is not about the value, but the association, causality each variable occupies in the equation.
- 8. 8 June 22, 2013 Dr Fayssal Farahat, MD 22 Frequency table التكراري الجدول Interval الفترة Frequency التكرار Valid % المئوية النسبة Cumulative % التراكمية النسبة <20 20-29 30-39 40-49 50-59 60-69 70-79 80-89 ≥90 Total 46 70 108 106 74 72 42 29 33 580 7.9 12.1 18.6 18.3 12.8 12.4 7.2 5.0 5.7 100.0 7.9 20.0 38.6 56.9 69.7 82.1 89.3 94.3 100 Few 6-14 Overlap 40-49, 49-50 Equal width Avoid open-ended Cumulative %= Obs % + all lower % <60 June 22, 2013 Dr Fayssal Farahat, MD 23 City Male smokers المدخنون Taif Riyadh Jeddah TOTAL Table (1). Number and percent of male smokers less and more than 18 ys old in different cities < 18 years > 18 years n % n % 80 90 150 320 TOTAL n % 40 30 30 32 120 210 350 680 60 70 70 68 200 100 300 500 1000 100 100 100 Tables June 22, 2013 Dr Fayssal Farahat, MD 24 Tables City Male smokers Taif Riyadh Jeddah TOTAL Table (1). Number and percent of male smokers less and more than 18 ys old in different cities < 18 years > 18 years n % n % 80 90 150 320 TOTAL n % 25 28 47 100 120 210 350 680 18 31 51 100 200 20 300 500 1000 30 50 100
- 9. 9 June 22, 2013 Dr Fayssal Farahat, MD 25 2 x 2 Exposure Smoker Non-smoker Cancer Lung Positive N (%) Negative N (%) June 22, 2013 Dr Fayssal Farahat, MD 26 Graphs Line graph Frequency Histogram Frequency polygon Bar chart Pie chart Pictogram June 22, 2013 Dr Fayssal Farahat, MD 27 Time Positive No relation Negative Variable X Y + - 0
- 10. 10 June 22, 2013 Dr Fayssal Farahat, MD 28 X Y Equal width June 22, 2013 Dr Fayssal Farahat, MD 29 Frequency Polygone التكراري المنحنى June 22, 2013 Dr Fayssal Farahat, MD 30 heal thy disease group 2 4 6 8 10 Count Healthy Diseased Count
- 11. 11 June 22, 2013 Dr Fayssal Farahat, MD 31 39.7 58.8 gp 1 gp 2 Age June 22, 2013 Dr Fayssal Farahat, MD 32 Sex distribution in different studied groups 0 10 20 30 40 50 60 70 80 Control Asthmatic COPD % Male Female June 22, 2013 Dr Fayssal Farahat, MD 33 healthy disease group Pies show counts Pie 44.44% 8.055.56% 10.0 Pie Chart
- 12. 12 June 22, 2013 Dr Fayssal Farahat, MD 34 Pictogram 1970 1980 1990 2000 June 22, 2013 Dr Fayssal Farahat, MD 35 0 2 4 6 8 10 12 14 Y1950 Y1960 Y1970 Y1980 Y1990 Y2000 Year Mortality(per1000) 2 4 6 8 10 12 14 0 1 2 3 4 1970y 1980y 1990y 2000y June 22, 2013 Dr Fayssal Farahat, MD 36 Summarizing qualitative data Proportion a / a + b (part / whole) Percentage Proportion X 100% Ratio a / b (part / another part) Rate a / a + b X base (1000, 10,000,100,000) + In a specific time (20 per 10,000 per year)
- 13. 13 June 22, 2013 Dr Fayssal Farahat, MD 37 Arithmetic Mean ExtremesHR variation 1 2 3 4 5 6 7 8 9 10 19.2 51.9 33.1 86.7 29.1 45.3 16.4 85.7 18.9 42.6 42.9 32.1 Consider each variable X June 22, 2013 Dr Fayssal Farahat, MD 38 Weighted Mean Interval Frequency Valid % Cumulative % 2-20 21-30 31-40 41-50 51-60 61-70 71-80 81-90 >90 Total 46 70 108 106 74 72 42 29 33 580 7.9 12.1 18.6 18.3 12.8 12.4 7.2 5.0 5.7 100.0 7.9 20.0 38.6 56.9 69.7 82.1 89.3 94.3 100 [(11 x 46) + (25 x 70) + ….+ (85 x 29) + (100 x 33)] / 580 = 49.1 X ? June 22, 2013 Dr Fayssal Farahat, MD 39 Median Middle observation Odd Even Extremes Consider each variable Ordinal data
- 14. 14 June 22, 2013 Dr Fayssal Farahat, MD 40 Mode Most frequent value Uni-modal Bi-modal Most frequent interval Most frequent diagnosis June 22, 2013 Dr Fayssal Farahat, MD 41 Measures of Spread التشتت مقاييس Range SD CV Percentiles Interquartile Range المدى المعياري االنحراف التغير معامل Percentiles الربعي المدى June 22, 2013 Dr Fayssal Farahat, MD 42 The Range The largest – the smallest
- 15. 15 June 22, 2013 Dr Fayssal Farahat, MD 43 June 22, 2013 Dr Fayssal Farahat, MD 44 Coefficient of Variation التغير معامل Measure 1 70 (31) Measure 2 105 (48) Can we Compare 2 different scales 2 different investigators CV = (SD / Mean) x 100 44.3 % 45.7 % Quality Control June 22, 2013 Dr Fayssal Farahat, MD 45
- 16. 16 June 22, 2013 Dr Fayssal Farahat, MD 46 Interquartile Range الربعي المدى = the difference between the 25th and 75th percentiles 25th 75th Central 50% 6.5 kg 7.5 kg 1st 3rd June 22, 2013 Dr Fayssal Farahat, MD 47 STEM الساق LEAF الورقة 2 3 4 5 6 5689 0011369 0269 03 027 30.00 33.00 31.00 29.00 30.00 31.00 26.00 28.00 36.00 39.00 40.00 49.00 50.00 60.00 67.00 46.00 42.00 25.00 62.00 53.00 Stem and Leaf Plot June 22, 2013 Dr Fayssal Farahat, MD 48 Box – and whisker plot
- 17. 17 June 22, 2013 Dr Fayssal Farahat, MD 49 Normal Distribution Curve Gaussian Distribution Curve June 22, 2013 Dr Fayssal Farahat, MD 50 Mean Median Mode Bell Shape 68% Symmetric June 22, 2013 Dr Fayssal Farahat, MD 51 Mean Median Mode Bell Shape 95% Symmetric
- 18. 18 Normal curves (μ=0, σ2=1) and (μ=5, σ 2=1) -2 0 2 4 6 8 x 0.00.10.20.30.4 fx1 Normal curves (μ=0, σ2=1) and (μ=0, σ2=2) -3 -2 -1 0 1 2 3 x 0.00.10.20.30.4 y Normal curves (μ=0, σ2=1) and (μ=2, σ2=0.25) -2 0 2 4 6 8 x 0.00.20.40.60.81.0 fx1
- 19. 19 June 22, 2013 Dr Fayssal Farahat, MD 55 8 0 9 0 1 0 0 1 1 0 1 2 0 1 3 0 1 4 0 1 5 0 1 6 0 0 5 1 0 1 5 2 0 2 5 P e r c e n t P O U N D S 120 130110 68% of 100 = .68 x 100 = ~ 68 students 8 0 9 0 1 0 0 1 1 0 1 2 0 1 3 0 1 4 0 1 5 0 1 6 0 0 5 1 0 1 5 2 0 2 5 P e r c e n t P O U N D S 120100 95% of 100 = .95 x 120 = ~ 95 students 140130110
- 20. 20 8 0 9 0 1 0 0 1 1 0 1 2 0 1 3 0 1 4 0 1 5 0 1 6 0 0 5 1 0 1 5 2 0 2 5 P e r c e n t P O U N D S 120100 140130110 0 +1 +2-1-2 X Z 130 – 120 10 x – μ σ 8 0 9 0 1 0 0 1 1 0 1 2 0 1 3 0 1 4 0 1 5 0 1 6 0 0 5 1 0 1 5 2 0 2 5 P e r c e n t P O U N D S 120100 140130110 126 0 +1 +2-1-2 x – μ σ Looking up probabilities in the standard normal tableZ=0.60 Z=0.00
- 21. 21 What is the area to the left of Z=1.51 in a standard normal curve? Z=1.51 Z=1.51 Area is 93.45%