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dr.rahambacha@yahoo.com 03336422555
dr.rahambacha@yahoo.com
03336422555
Dr. Raham Bacha
Ultrasound specialist
MD, PhD Scholar
MSc Ultrasound (Gold Medalist)
Lecturer Afro-Asian Institute
Lahore
...
Research Methodology
&
Biostatistics.
Respected readers it is mandatory for every researcher to know
somewhat about resear...
What is Research?
• Research is composed of two worlds.
“Re” mean again
And
Search mean to find new facts
It means to sear...
Webster international Dictionary
proposed a very inclusive definition.
“A careful inquiry or examination in seeking
facts ...
It starts with a problem, collects
data (facts and figures) analyses
these critically based decisions of
actual evidence. ...
• Don’t appreciate the research of other and
yourself.
• Develop critical thinking.
• Specialized tools and instruments (M...
Research provides:
1. Analytic framework for subject matter
investigation
2. Establishes relationship between different
va...
Important points
• Research should not be treated as a place
of compilation work. It is not simply the
compilation of mate...
STATISTICS
numerical facts in any field of study.
It concerns with collection, organization,
summarization, analysis and d...
dr.rahambacha@yahoo.com 03336422555
Bio-statistics
Bio-statistics is the branch of statistics that concerns
with the appli...
dr.rahambacha@yahoo.com 03336422555
In medical field, statistical methods enable us to
check the effectiveness of differen...
dr.rahambacha@yahoo.com 03336422555
Being medical students often we need to
study research paper or we need to present
our...
dr.rahambacha@yahoo.com 03336422555
Central Tendency
Central tendency is a characteristic of a data set
which relates to i...
dr.rahambacha@yahoo.com 03336422555
MEAN
The most commonly used measure of central tendency. It is
the sum of all the obse...
dr.rahambacha@yahoo.com 03336422555
Median
The median of a set of data arranged in order of
magnitude is the middle most v...
dr.rahambacha@yahoo.com 03336422555
Rates
The number of events in a population in specific time.
Suppose, in a specified p...
dr.rahambacha@yahoo.com 03336422555
Prevalence Rate (P.R.)
Prevalence rate of an attribute or event in any group, is the
p...
dr.rahambacha@yahoo.com 03336422555
Incidence Rate (I.R.)
The risk of developing the disease over a period of time is
call...
dr.rahambacha@yahoo.com 03336422555
Measures of Dispersion
The measure of spread of data/observations from its
averages. S...
dr.rahambacha@yahoo.com 03336422555
Range
Range is the difference between maximum and minimum
values of data set
Standard ...
dr.rahambacha@yahoo.com 03336422555
The most pleasurable moment of my life, when I was awarded with Gold medal
dr.rahambacha@yahoo.com 03336422555
Share feelings with media.
Dr. Raham Bacha Ultrasound Specilist
The Statistical
Profile
25
The Statistical Profile
These include;
1. sensitivity,
2. specificity,
3. positive predictive value, and
4. negative predi...
These terms are defined as follows:
1. Sensitivity (True Positive Ratio or Rate):
The ability of a test to find disease wh...
These terms are defined as follows:
4. Negative Predictive Value (NPV):
NPV is a measure of how likely it is that disease ...
The Chi Square Test
This test brings together the statistical terms discussed
above. In the Chi Square, data from any test...
The Chi Square Test
Gold Standard result
Our testing
modality
result
present + absent
+
Positive + A B
Negative - C D
Dr. ...
The Chi Square Test
Formulas for statistical terms:
1. Accuracy = (A+D)/ A+B+C+D
2. Sensitivity = A/ (A+C)
3. Specificity ...
Chi Square Example
Let’s take a few moments to work through an example
using the Chi square.
Suppose 100 non-invasive vasc...
Chi Square Example
Let’s create a Chi square to illustrate the data above.
NON-
INVASIVE
VASCULAR
TEST
Gold Standard
prese...
Chi Square Example
The chart above illustrates the results of the 100 tests performed
on our patients.
Note that the 55 to...
Chi Square Example
Accuracy = (A+D)/A+B+C+D
= (50+35)/50+5+10+35
= 0.85 x100
= 85%
Dr. Raham Bacha Ultrasound Specilist 35
Chi Square Example
Sensitivity = A / (A+C)
= 50/(50+10)
=50/60
= 0.83
= 0.83x100
= 83%
Dr. Raham Bacha Ultrasound Specilis...
Chi Square Example
Specificity = D/ (B+D)
= 35/ (5+ 35)
= 35 / 40
=0.88
= 88%
Dr. Raham Bacha Ultrasound Specilist 37
Chi Square Example
Positive predictive value = A/ (A+B)
=50/ (50+5)
= 50/55
=0.91
= 0.91 X 100
= 91%
Dr. Raham Bacha Ultra...
Chi Square Example
Negative Predictive Value = D/ (C+D)
= 35/ (10+35)
= 35/45
= 0.78
= 78%
Dr. Raham Bacha Ultrasound Spec...
Test Goals
The purpose of any of the non-invasive tests discussed in this
course is to identify disease when it is present...
Test Goals
The predictive value of a positive or negative test result is
perhaps the most useful expression of accuracy as...
study
dr.rahambacha@yahoo.com 03336422555
Who knew that statistics could be this much fun!
Dr. Raham Bacha 43
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Research methodology and biostatistics

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Condense lecture which enable us to read some one research easily and make inferences from the data with the help of SPSS software

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Research methodology and biostatistics

  1. 1. dr.rahambacha@yahoo.com 03336422555
  2. 2. dr.rahambacha@yahoo.com 03336422555
  3. 3. Dr. Raham Bacha Ultrasound specialist MD, PhD Scholar MSc Ultrasound (Gold Medalist) Lecturer Afro-Asian Institute Lahore dr.rahambacha@yahoo.com 03336422555
  4. 4. Research Methodology & Biostatistics. Respected readers it is mandatory for every researcher to know somewhat about research and biostatistics. But unfortunately we have been teach by biostatisticians in our universities and medical schools. They want to make us biostatistician and teach us thoroughly. I therefore felt a need to prepare a lecture in condense form which make enable us to know those terms which are frequently used in research results. The purpose of the lecture is to read and understand some research and even analyze your research data and make inferences with the help of SPSS software. dr.rahambacha@yahoo.com 03336422555
  5. 5. What is Research? • Research is composed of two worlds. “Re” mean again And Search mean to find new facts It means to search again new facts or To modify older ones, in any branch of knowledge. dr.rahambacha@yahoo.com 03336422555
  6. 6. Webster international Dictionary proposed a very inclusive definition. “A careful inquiry or examination in seeking facts or principles, diligent investigation in order to ascertain something.” Crawford Says: “Research is simply a systematic and refined technique of thinking, employing specialized tools, instruments & procedures in order to obtain a more adequate solution of a problem than would be possible under ordinary means.” dr.rahambacha@yahoo.com 03336422555
  7. 7. It starts with a problem, collects data (facts and figures) analyses these critically based decisions of actual evidence. It evolves original work instead of mere exercise of personal opinion (theory). It is quantitative and measurements is therefore a central feature of it. dr.rahambacha@yahoo.com 03336422555
  8. 8. • Don’t appreciate the research of other and yourself. • Develop critical thinking. • Specialized tools and instruments (Material i.e. data sheets) In fact research is treated as advancement in knowledge acquired through scientific methods dr.rahambacha@yahoo.com 03336422555
  9. 9. Research provides: 1. Analytic framework for subject matter investigation 2. Establishes relationship between different variables e.g. cause and effect relationship, Co-relationship between variables. dr.rahambacha@yahoo.com 03336422555
  10. 10. Important points • Research should not be treated as a place of compilation work. It is not simply the compilation of material taken from different books and sources. It is always expected to something original that advances some knowledge. • Research should be very clear in Researcher mind that he is going to do. • The domain of Research problem must be clear. dr.rahambacha@yahoo.com 03336422555
  11. 11. STATISTICS numerical facts in any field of study. It concerns with collection, organization, summarization, analysis and drawing inferences from a data set. the science comprising methods, which are used in collection, presentation, analysis, and interpretation of numerical data (information). dr.rahambacha@yahoo.com 03336422555
  12. 12. dr.rahambacha@yahoo.com 03336422555 Bio-statistics Bio-statistics is the branch of statistics that concerns with the applications of statistical methods to medical and biological data.
  13. 13. dr.rahambacha@yahoo.com 03336422555 In medical field, statistical methods enable us to check the effectiveness of different testing modalities in medicines. Recently, it has been found that applications of statistical methods in medical data are very effective. Testing of hypothesis, analysis of variance, chi-square, non- parametric methods, regression and correlation, logistic regression etc. are frequently used in the analysis of health and medical data.
  14. 14. dr.rahambacha@yahoo.com 03336422555 Being medical students often we need to study research paper or we need to present our research work in statistical terms. It is therefor needed to know some of the fundamental terms frequently used in research papers. Significance of Bio-Statistics in Medical.
  15. 15. dr.rahambacha@yahoo.com 03336422555 Central Tendency Central tendency is a characteristic of a data set which relates to its average value. Most commonly used measures are,  Mean  Median and mode  Quartiles  Deciles  Percentiles
  16. 16. dr.rahambacha@yahoo.com 03336422555 MEAN The most commonly used measure of central tendency. It is the sum of all the observation divided by the number of observation is mean. nsobservatioofnumbertotal setdataofnsobservatiotheallofsum Mean 
  17. 17. dr.rahambacha@yahoo.com 03336422555 Median The median of a set of data arranged in order of magnitude is the middle most value. Mode Mode is the most frequently occurring number in the data set.
  18. 18. dr.rahambacha@yahoo.com 03336422555 Rates The number of events in a population in specific time. Suppose, in a specified population “n” events occur during a fixed period of time n(A). If n(A) of these events possess some characteristic, say A, then rate of the event having the characteristic A is given by 𝑹𝒂𝒕𝒆 = 𝒏(𝑨) 𝒏
  19. 19. dr.rahambacha@yahoo.com 03336422555 Prevalence Rate (P.R.) Prevalence rate of an attribute or event in any group, is the proportion of individuals in the groups having that attribute at one point in time. This is also known a prevalence ratio. K groupinsindividualofnumbertotal timegivenaatdiseaseorattributewithsindividualofnumber RP .
  20. 20. dr.rahambacha@yahoo.com 03336422555 Incidence Rate (I.R.) The risk of developing the disease over a period of time is called incidence rate and is calculated as: K groupinsindividualofnumbertotal timegivenaatofdiseasecasesnewofnumber RI .
  21. 21. dr.rahambacha@yahoo.com 03336422555 Measures of Dispersion The measure of spread of data/observations from its averages. Statistical measures of dispersion are used to measure the extent to which individual observations disperse or cluster around the average. two commonly used measures are; range and standard deviation.
  22. 22. dr.rahambacha@yahoo.com 03336422555 Range Range is the difference between maximum and minimum values of data set Standard Deviation The most widely used and stable measure of dispersion is the standard deviation. This is a square root of variance.
  23. 23. dr.rahambacha@yahoo.com 03336422555 The most pleasurable moment of my life, when I was awarded with Gold medal
  24. 24. dr.rahambacha@yahoo.com 03336422555 Share feelings with media.
  25. 25. Dr. Raham Bacha Ultrasound Specilist The Statistical Profile 25
  26. 26. The Statistical Profile These include; 1. sensitivity, 2. specificity, 3. positive predictive value, and 4. negative predictive value. 5. accuracy, 6. reliability Dr. Raham Bacha Ultrasound Specilist 26
  27. 27. These terms are defined as follows: 1. Sensitivity (True Positive Ratio or Rate): The ability of a test to find disease when disease is present. 2. Specificity (True Negative Ratio or Rate): The ability of a test to indicate no disease when there is no disease present (i.e. to exclude disease when a patient is normal. 3. Positive Predictive Value (PPV): PPV is a measure of how likely it is that disease is actually present when the test result is positive. In other words, it is the proportion of people with a positive test who actually have the disease. Dr. Raham Bacha Ultrasound Specilist 27
  28. 28. These terms are defined as follows: 4. Negative Predictive Value (NPV): NPV is a measure of how likely it is that disease is actually absent when the test result is negative. In other words, it is the proportion of people with a negative test who are free of disease. 5. Accuracy: The ability of a test to give the correct answer. 6. Reliability: Consistency in obtaining similar results in similar circumstances. Dr. Raham Bacha Ultrasound Specilist 28
  29. 29. The Chi Square Test This test brings together the statistical terms discussed above. In the Chi Square, data from any test is compared to data obtained using the gold standard. In graphical form, the Chi square looks like this: Dr. Raham Bacha Ultrasound Specilist 29
  30. 30. The Chi Square Test Gold Standard result Our testing modality result present + absent + Positive + A B Negative - C D Dr. Raham Bacha Ultrasound Specilist 30
  31. 31. The Chi Square Test Formulas for statistical terms: 1. Accuracy = (A+D)/ A+B+C+D 2. Sensitivity = A/ (A+C) 3. Specificity = D/ (B+D) 4. Positive Predictive Value = A / (A+B) 5. Negative predictive value = D/ (C+D) Dr. Raham Bacha Ultrasound Specilist 31
  32. 32. Chi Square Example Let’s take a few moments to work through an example using the Chi square. Suppose 100 non-invasive vascular tests were performed in the vascular lab on patients who also had an arteriogram (considered the gold standard in this case). The non- invasive test yielded 55 positive results and 45 negative results. Of the 55 positive tests the arteriogram found 5 to be negative and of the 45 negative tests, the arteriogram found 10 to be positive. Dr. Raham Bacha Ultrasound Specilist 32
  33. 33. Chi Square Example Let’s create a Chi square to illustrate the data above. NON- INVASIVE VASCULAR TEST Gold Standard present + absent + Total Positive + 50 5 55 Negative - 10 35 45 Total 60 40 100 Dr. Raham Bacha Ultrasound Specilist 33
  34. 34. Chi Square Example The chart above illustrates the results of the 100 tests performed on our patients. Note that the 55 total positive exams by the non-invasive test are broken down to indicate the ones with which the gold standard agreed and disagreed. Also note that the total of all four squares must equal the total number of tests performed (i.e. 100 in our example. Now let’s perform the calculations required for each of the six statistical formulas discussed previously. (Multiply the results by 100 in order to arrive at a percent.) Dr. Raham Bacha Ultrasound Specilist 34
  35. 35. Chi Square Example Accuracy = (A+D)/A+B+C+D = (50+35)/50+5+10+35 = 0.85 x100 = 85% Dr. Raham Bacha Ultrasound Specilist 35
  36. 36. Chi Square Example Sensitivity = A / (A+C) = 50/(50+10) =50/60 = 0.83 = 0.83x100 = 83% Dr. Raham Bacha Ultrasound Specilist 36
  37. 37. Chi Square Example Specificity = D/ (B+D) = 35/ (5+ 35) = 35 / 40 =0.88 = 88% Dr. Raham Bacha Ultrasound Specilist 37
  38. 38. Chi Square Example Positive predictive value = A/ (A+B) =50/ (50+5) = 50/55 =0.91 = 0.91 X 100 = 91% Dr. Raham Bacha Ultrasound Specilist 38
  39. 39. Chi Square Example Negative Predictive Value = D/ (C+D) = 35/ (10+35) = 35/45 = 0.78 = 78% Dr. Raham Bacha Ultrasound Specilist 39
  40. 40. Test Goals The purpose of any of the non-invasive tests discussed in this course is to identify disease when it is present and exclude it when it is absent. Whether we are in Search of atherosclerosis or venous thrombosis, we strive to produce the most accurate result within our capabilities. In order to confirm or dispute the results of non-invasive tests, our results are often compared with an established diagnostic test known as the gold standard. In cerebrovascular diagnosis, the current gold standard is the angiogram. In the study of vascular disease, the venogram is still the gold standard. Dr. Raham Bacha Ultrasound Specilist 40
  41. 41. Test Goals The predictive value of a positive or negative test result is perhaps the most useful expression of accuracy as far as the referring physician is concerned. It is essential that we remember that the skill of the vascular technologist may be crucial in attaining accurate test results. I am sure that is why we all study so hard to become excellent in the performance of our examinations. Dr. Raham Bacha Ultrasound Specilist 41
  42. 42. study dr.rahambacha@yahoo.com 03336422555 Who knew that statistics could be this much fun!
  43. 43. Dr. Raham Bacha 43

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