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Biostatistics-Exam 2 Full Study Guide

by: A Jones

Biostatistics-Exam 2 Full Study Guide Heal 395

Marketplace > College of Charleston > Public Health > Heal 395 > Biostatistics Exam 2 Full Study Guide
A Jones
C of C
GPA 3.5

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I have completed study guides for Exam 1 and 2. I did very well in the course by creating and using these in depth notes. Goodluck!
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This 10 page Study Guide was uploaded by A Jones on Friday September 9, 2016. The Study Guide belongs to Heal 395 at College of Charleston taught by Hart in Fall 2016. Since its upload, it has received 6 views. For similar materials see Biostatistics in Public Health at College of Charleston.


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Date Created: 09/09/16
9/5/2016 Exam 2 | Evernote Web Exam 2 Normal Distribution Probability Estimation­f601­42cf­abe1­1595d1fe041f&b=3e793d12­1/10­48b5­aeeb­12b02ed6bc73&ses=4&sh=1&sds=5& 9/5/2016 Exam 2 | Evernote Web Standard deviation formula: What does the z score represent? relationship to the mean in a group of scores: can also be positive or negative, indicating whether it is above or below the mean and by how many standard deviations.     Negative: probability values are less than­  The Z score for a weight =100lbs is: ᵄᵄ(100) = (100−150) 30 = ­1.67 The probability associated with a Z score of ± 1.67 is 0.047.­f601­42cf­abe1­1595d1fe041f&b=3e793d12­ce29­48b5­aeeb­12b02ed6bc72/10s=4&sh=1&sds=5& 9/5/2016 Exam 2 | Evernote Web Therefore, this probability means that based on these data, there is a 0.047 (4.7%) chance that a person will weigh less than 100 lbs.     Positive: probability values are more than­  How to calculate z score:     **** population: mu and sigma: μ & σ Example: μ = 150 mg/dL σ = 30 mg/dL  150­(2*30) = 90 150+(2*30) = 210 This means 68%of the values fall between 90 and 210  Central Limit Theorem­ as sample size increases the distribution of averages are more normal Binomial Distribution Probability Estimation ­Discrete Binomial Probabilities ­Cumulative Binomial Probabilities­f601­42cf­abe1­1595d1fe041f&b=3e793d13/1029­48b5­aeeb­12b02ed6bc73&ses=4&sh=1&sds=5& 9/5/2016 Exam 2 | Evernote Web ­When do we use the Normal Approximation to the Binomial Distribution? When do we use the Binomial Distribution to estimate the probability of something? dichotomous variables Poisson Distribution Probability Estimation ­Use for discreet/rare events  ­Collected over area, distance, time  ­Events are independent  ­More events as time intervals increase  Pr (x=x|lambda)=­f601­42cf­abe1­1595d1fe041f&b=3e793d12­4/10­48b5­aeeb­12b02ed6bc73&ses=4&sh=1&sds=5& 9/5/2016 Exam 2 | Evernote Web lambda = mean # of events     ­key words: average, mean, expected x= random # we're interested in ***Cumulative Probability: If you want to know the probability of 7 rooms or less, you would calculate: Pr(7) + Pr(6) + Pr(5) + Pr (4) + Pr(3) + Pr(2) + Pr(1) + Pr(0) Screening Tests: Sensitivity, Specificity, Positive Predictive Value, Negative Predictive Value Sensitivity of screening tests: probability test in positive given that the disease is positive. ACCURACY How good is the test at detecting the diseaseFormula: Pr(T+|D+) True positives      Interpretation: This _______ screening test will detect actual cases of __________    ##% of the time. Specificity of screening tests: probability test is negative given that the disease is negative. ACCURACY How good is the test at detecting those w/o the disease True negatives      Formula: Pr(T­|D­) Interpretation: A negative result from this ________ screening test will indicate that you do not have ________ ##% of the time. Positive Predictive Value of a Screening Test PREDICTION probability of having the condition given a positive screening test 2 numbers on the top, 4 on the bottom      Interpretation: There is a ##% chance that you have a condition given a positive result from the screening test.­f601­42cf­abe1­1595d1fe041f&b=3e793d12­ce5/108b5­aeeb­12b02ed6bc73&ses=4&sh=1&sds=5& 9/5/2016 Exam 2 | Evernote Web Negative Predictive Value of a Screening Test PREDICTION probability of NOT having the condition given a negative screening test 2 numbers on the top, 4 on the bottom Interpretation: There is a ##% chance that you DO NOT have a condition given a negative result from the screening test     Descriptive Studies: Cross­Sectional, Ecologic/Correlation, Case Series/Case Study­f601­42cf­abe1­1595d1fe041f&b=36/10d12­ce29­48b5­aeeb­12b02ed6bc73&ses=4&sh=1&sds=5& 9/5/2016 Exam 2 | Evernote Web Descriptive  epi studies goal: describe health related states or events with regards to person, place and time measure the Magnitude and Frequency of both Exposures and Outcomes 3 types of descriptive epi studies 1. Cross­Sectional, 2. Ecologic/Correlation 3. Case Series/Case Study Cross Sectional Study What is Cross sectional study used for? snapshot of exposures and/or outcomes among individuals at a single point in time usually via a single survey with no follow­up tell us magnitude or frequency­f601­42cf­abe1­1595d1fe041f&b=3e793d12­ce29­48b5­aeeb­7/102ed6bc73&ses=4&sh=1&sds=5& 9/5/2016 Exam 2 | Evernote Web Upper 95 % CI + Prevalence +(1.96 √(prevalence*1­prevalence)/ (sample size) Lower 95 % CI ­  Prevalence +(1.96 √(prevalence*1­prevalence)/ (sample size) ***CI measures precision of the sample, how close are the results from the sample from the population? Strengths of Cross sectional Inexpensive Can study several exposures or outcomes at once Short duration  Establish a foundation for additional/future hypotheses and analytic studies Weaknesses of Cross sectional Cannot establish cause and effect Cannot establish temporality. In other words, we cannot determine if exposure occurred before outcome?  Those who respond or participate are probably different than those who do not *****Serial Survey: Cross­sectional survey that is conducted over a period of time Correlational / Ecologic Studies (exposures and outcomes) of  groups  measurement: correlation coefficient (linear relationship) Ecologic Fallacy­ false impression that observed conclusions for the group hold true for the individual Case Studies Summary of an individual’s health, information/experience (good for something new) Including: Demographics, Spatial, Social, Symptoms, and Exposures Case Series Collection of health profiles/summaries for individuals with similar exposures or outcomes  Goal: helps define case definition­f601­42cf­abe1­1595d1fe041f&b=3e793d12­ce29­48b58/10b­12b02ed6bc73&ses=4&sh=1&sds=5& 9/5/2016 Exam 2 | Evernote Web Analytic Studies: Cohort and Case­ Control Case­Control Studies selected based on if they have the disease or not good for diseases  that take a long time to develop compare exposed and those not exposed by comparing the proportion of exposure math: exposed or not exposed/total in study Put CC Contingency table in notes (know a,d,c,d) Odds ratio (AD/BC) ­know odds ratio interpretation    ­know odds ratio confidence interval    ***TIP: odds ratio should be between upper and lower limit ­know Odds ratio statistical significance sentence Cohort Studies selected based on exposure prospective: look for outcome in the future b/c outcome has not occured retrospective: outcome has already occurred so outcome status is known know cumulative incidence know incidence rate (remove people who have already had the disease) define relative risk & know equation know relative risk interpretation greater than 1=subtract 1 less than 1, multiply by 100%   know relative risk confidence interval equations  Incidence­ tells us about magnitude­f601­42cf­abe1­1595d1fe041f&b=3e793d129/109­48b5­aeeb­12b02ed6bc73&ses=4&sh=1&sds=5& 9/5/2016 Exam 2 | Evernote Web­f601­42cf­abe1­1595d1fe041f&b=3e793d12­ce29­48b5­aeeb­12b02ed6bc73&ses=4&sh=1&sds=5& 10/10


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