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28 Cards in this Set
- Front
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are outliers reflected in the mean value (arrange all numbers, pick the middle one)
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no, it better represents data that is skewed...ex professor ranking, if class is small median is better
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null hyp
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states no difference in 2 groups (drug a = drug b)
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P value
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probability that obtaining a test statistic as extreme as the one that was actually observed, assuming null hypothesis is true.
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type 1 error
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null hyp is tue, yet rejected in error. prob of type 1 error is represented by alpha. is it is 5%then 5% of the time the null hypothesis will be rejected in error, falspe positive (court finds an innocent person guilty and sends them to jail)
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type 2 error
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null hyp is false yet accepted in error... we conclude there is no difference when there actually is a difference. prob of making a type 2 error is Beta
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2 types of variables?
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discrete, continuous rando
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def of discrete variable?
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nominal and ordinal:
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nominal?
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can be divided into groups or categories (marital status, gender, ethnicity)
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ordinal?
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usually a scoring system (ex likert scale) cannot be measured/quantified. ex a trauma score of 4 is not necessarily twice as big as a score of 2
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continuous random variable?
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ex height weight, can presumably take an infinite amound of possible values, can be fractions
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statistical power?
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prob that the null hyp will be rejected if it is false. a higher statistical power means that we can be more certain that the null hypothesis was not rejected incorrectly or achieve a lower type 1 error
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confidence interval?
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statistical range with a specified probability that a given parameter lies within the range or said another way, the porportion of times that an estimate will be correct. if CI is 95% it means that 95% of the time, you are confident that the parameter will fall in this range
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Odds ratio?
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ex. if there are 100 people, 40 people had an event and 60 didnt...40/60=0.66...odds ratio of 1 is no difference in the groups
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Relative risk or risk ration
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ratio of risk in the treatment group to the risk in the control group
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standard deviation def
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the SD is a statistic that tells you how tightly all the various examples are clustered around the mean in a set of data
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if SD is normal distribution?
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68% of values are within 1 SD, 95% are within 2 SDb
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when is SD appropriate?
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if normal distribution continuous data
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interquartile range (IQR)
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difference between the 1st quartile (25th percentile) and the 3rd quartile
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Standard error of the mean (SEM)
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estimate of the standard deviation, taken from a sample group
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case control study? look forward or back?
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retrospective, cased used of stubjects with the intervention and controls, cases compared to the controls
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cohort study? look forward or back?
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prospective, study group (cohort) follwoed over time and outcomes are copared to a subset that were not exposed to the intervention
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controlled clinical trial
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study group compared in a controlled setting
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Gold standard for doing a clinical drug trial is a randomized placebo controlled double blinded multicenter trial with adequate statistically power (p value under 0.05)
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ture
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cross sectional study?
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for ex. if people who have smoked for a given period of time have a higher incidence of heart diseaseat 2 years
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frequency distribution
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used for lists of data ranked from lowest to highest
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histogram
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tabulated frequencies, shown as bars
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what is regression
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ability for 1 or more variables to predict another (risk of GI bleeding in pts on high dose chronic nsaids)
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multiple regression
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involves many predictors that can affect a variable, and there will be many r values. this means that regression can be used to hold one value constant, so that is doesnt affect other variables. regression models to control for confounding variables is common in drug studies
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