Short Story• Ahmed, A young man accused by robbing a supermarket. arrested by the police and charges where pressed by the attorney general.• attorney general is claiming that Ahmed robbed the supermarket• Ahmed heirs an attorney to defend him. and prove him innocent• Two possibilities: • he robbed it • he didn’t But whats the plan, How can we now the truth
In Court• In order for the Attorney general to lock him away he needs to prove him “Guilty”• The Attorney Genaral needs to prove that Ahmed is not innocent• In Order for Ahmed to be set free his lawyer needs to Stop him from doing so• The lawyer doesnt need to prove that Ahmed is innocent
Lets Think about it• Hypothesis = Claim• Attorney Genaral is claiming that Ahmed robbed the supermarket• His Hypothesis is “Ahmed Robbed the Supermarket”• He is Trying to prove it by Rejecting the idea that “ Ahmed did not rob the Supermarket• if he dose succeed. we will by left with one conclusion that Ahmed did rob the supermarket• If he doesnt succeed. The two possibilities are still their. And we can’t send Ahmed to jail because we are not sure
AhmedThis is what Robbed The Supermarket Did Not rob the Supermarketthe Attorneygeneralwants
AhmedThis Is what Robbed The Supermarket Did Not rob the SupermarketAhmed’sLawyer • You Can not convect a person unless your surewants • Its better to send a guilty man free, than or send an innocent man to jail • Benefit of the doubt
Inferential Statistics• I’m Assuming that i will score a full mark in the USMLE exam• This assumption has a very rare probability• Then this assumption is not true
Lets put it into scientific terms• If you want to prove something, you need to formulate a hypothesis• Your assumption (hypothesis) called the (Alternative Hypothesis) H1 Rare Event Rule for Inferential Statistics• The opposite called the (Null Hypothesis) H0• You Try to prove the the null hypothesis only happens very rarely
HypothesisThis is what Alternative Hypothesis (H1) Null Hypothesis H0the Attorneygeneralwants
HypothesisThis is what Alternative Hypothesis (H1) Null Hypothesis H0theInvestigatorwants
HypothesisTHA is Alternative Hypothesis (H1) Null Hypothesis H0Superior toBipolar in THA is True There Is NoNOF Superior Difference
Example• The Journal of Bone and Joint Surgery 2010;92:792.• Assuming there is “deference Between Gamma nail and DHS” • H1 : No difference • H0: there is difference• Conclusion : “They are the Same”
Hypothesis Alternativ Null e Hypothesi Hypothesi s (H0) s (H1)There is No There Is a difference difference Between betweenGamma and Gamma DHS and DHS
Inferential Statistics• You Can not prove something to be true, But you can disapprove something by finding an exception No, I All swans found a are white black one
Example• Wrong Hypothesis• Wrong Results• Wrong Conclusion• Wasted 8 years of hard Work This is the JBJS after all
Not Everything youRead is Correct• We ended up responding to JBJS pointing out this huge fault
• Rare Event Rule for Inferential Statistics: If, under a given assumption, the probability of a particular observed event is exceptionally small, we conclude that the assumption is probably not correct.InferentialStatistics
How rare is rare?• The is a pre-determined value.• The probability of the H0 being true• It could be any number• In clinical studies its 0.05• in pharmaceutical studies its 0.01• Some times its call the critical value• its a cut-off for making a decision about the Null Hypothesis
Probability Value• What is the probability that of getting this result by chance?• What is the probability of getting this Sample that show this result?• You could be unlucky and have a very unfortunate sample?• Or that is the real probability of getting this set of data
P-Value, Is That Enough• How sure are you?• If we repeat the experiment 100 times. Each time taking a sample, will we have the same P-Value?
Confidence Interval at 95%• Your a Resident sitting for the promotion exam• Your score was 70%• Take the test again for 100 times• Scores ranged from 60-80%• Now I can say That • If you take the exam 100 times, I’m 95% Confidant that you will score any mark between 60-80 • In other words 70 -10, +10
Confidence Interval at 95%• An experiment has been done comparing 50 subjects• Cemented THA vs non-Cemented THA• Rate of Failure 20% vs 10% after 10 years• P-Value 0.04• Looks Good, Doesnt Are You ? How Sure it ? What is your confidence Interval?
Confidence Interval at 95%• If Your repeat this experiment 100 times• Will you have the same P-Value?• CI 95% turned to be from 0.1 - 0.003
Confidence Interval at 95%• I am 95% sure that your score in the promotion exam will be from 0-100 • With a P-Value of 0.05• I’m 95% sure that your score will be from -10 to 50 • With a P-Value of P 0.000000001• I’m 95% sure that your score will be from 70-75 With a P-Value of 0.1
Confidence Interval at 95%• In any statistical test there is a C.I. for any value• The P-Value has no meaning without a CI• If there is no CI someone is hiding something
Confidence Interval at 95%• There is a CI for everything• Gluco check reader has a CI -5 +5• You got a reading of 7• That means if you repeat the reading again it could be 2 or 12• repeat it 100 times results will fall between 2-12 95% of the time
Power• The ability of the sample to detect a deference when its there• Power of 80% is accepted• That means: • That this sample can detect the intended difference if it exists 80% of the time
Heard About Type1, Type II Error• Type I: • You Reject the Null. when in fact its true • Probability of Having this Error is 0.05 • The call it the Alfa value • Sending an Innocent guy to Jail • Type II • Failing to Reject the Null. when in fact false • Probability of having it is 20% • Called Beta Error • Letting a guilty man lose
Why Do we Need One?• Medical Research Needs approval• Research costs money• Clear plan on: • What you want to do? • Why You want to do? • How you plan to do it?
Before You Write• Start with a novel idea• What research is funded by institute and program of interest?• passes the “So what ?” Test• Gather your software
Before You Write• Get to know the review criteria • Significance: Scientific & practical importance; Impact • Investigators: Expertise, training, accomplishments • Innovation: Challenge/shift current research/practice • Approach: Soundness of overall strategy, methods, analyses. anticipate problems, address risks • Environment: Institutional resources, equipment, access to special populations • Reviewers: Who are they?
Software• Word Processor: • Pages • Word • Open Office• Reference Maneger: • Endnote • Ref Works
What Is Known? Gap Goal / Propose Guiding Hypothesis Specific aimsIMPACT/EXPECTED OUTCOMES
Skeleton• Getting Started• Aims and Expected Outcomes• Background• Significance and Innovation• Research Plan, Methodology, Timing• Budget and its Justification• Benefits of Your Research
Introduction • What is this proposal about and what is its relevance for health . • What do we know about this issue? • What is the important gap in knowledge that you need to fill? • Why do you need to fill this gap?Why is it a significant problem worthy of funding to address? E.g., Why is it a barrier to progress in the field? )
Introduction• Critical evaluation of literature as it relates to proposed work and gap to be filled.• Cite key articles, update• Discuss any relevant controversies and how project will resolve• Provides rationale for the gap(s) you have identified, leads into your main hypothesis & preliminary studies• Significance: Expand on importance and impact mentioned in Specific Aims• Why is work significant? Specific benefits of the knowledge to be obtained?• How will these benefits: • fit with institutes mission?
Aims• Main hypothesis:• What is it? Why? (Is it derived from preliminary findings? Is it the best fit given the literature?)• Justification for the Proposed Research: Why is it important to do this particular research? How will it allow you to move to the next step?
Specific Aims• Lay out each specific aim & hypothesis for each.• Should follow closely from your overarching hypothesis.• Hypothesis-driven• Mechanism/process-oriented rather than descriptive
Specific Aims• What will your work buy us? • Innovation • Expected outcomes• What impact will your work have on the health- related problem and the field?
Solicit Comments• Colleagues• Revise• Program Director
• Create a writing timeline.• Be realistic!• 4-6 months (!!!)
Design & Methods • Describe how you will carry out the research • Must relate closely to your specific aims • Include details for specific methodology and why the chosen method is the best to accomplish your goals. • Organize by aim. • Troubleshoot: How will you avoid or handle potential problems? Alternatives?
Design & Methods • Statistical strategy (justify use of specific analytic techniques, power analysis) • Remember to include timetable for project • Key point: Justify everything!
Budget• Direct Costs • can be specifically documented, eg: • salaries; • operating expenses (printing, consumables); • travel (kilometerage, fares, lodging, sustenance); • equipment, ect
Budget• Indirect Costs • real costs that cannot be easily identified as specific to a particular project, eg: • utilities; • maintenance of space and equipment; • security; • computer services;• legal services;• accounting services;• payroll services.
Budget Justification• Justify every item. Do not merely restate proposed expenditure.• Explain why the project could not proceed/would not be successful without these items
Roles and responsibilities• Clearly explain what each participant in the project will be doing.
Authorship• Criteria for authorship: • Substantial contributions to conception and design, acquisition of data, or analysis and interpretation of data. • Drafting the article or revising it critically for important intellectual content. • Final approval of the version to be published.
Publishing• Its your proposal combined with your results• You should of had an Journal or conference in mind while in the designing phase• You will be rejected• Dose a fewer Authors mean better paper?• Target High Impact journals
Be Correct (in content & details) • Instructions (formatting, page limits, font, margins) • Sections in prescribed order • Proofread – eliminate typos, grammatical errors, etc. • Proofread again…and again