PROBABILIDAD Flashcards
(71 cards)
1
Q
Probabilidad objetiva y subjetiva
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2
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Empirical probability dado STATA
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3
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Binomial probability
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4
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Binomial probability
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5
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Binomial probability
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6
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Poisson
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7
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Poisson
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8
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9
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Bar graph binomial distribution
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10
Q
Poisson formula
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11
Q
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12
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En STATA
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13
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14
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15
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2 dice in STATA
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16
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PROBABILITY PROBLEM
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17
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18
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19
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STATA IS LEFTLIST
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20
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21
Q
Pnorm graphs to check normality should be used with… sample sizes
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Large
22
Q
In medicine we usually have a long R tail, so we use transformations of the variable so that they can follow a normal distribution
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23
Q
NORMAL DISTRIBUTION SUMMARY
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24
Q
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Random error
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Systematic error-bias
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Sampling in STATA
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Sampling in STATA
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Para no perder el trabajo cuando hacemos RANDOM SAMPLING IN STATA, debemos usar los comandos…
preserve
….
restore
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Count
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Random allocation “randomization”
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RANDOMIZATION IN STATA
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What can you do to get again exactly the same random allocation or the same random sampling in STATA?
Set seed 9999
33
In internal validity, what is more important? Biological inference or statistical respresentativeness?
BIOLOGICAL INFERENCE: for causal inference.
Representativeness can become a fallacy and it is needed for external validity.
34
REPLICAR EL CENTRAL LIMIT THEOREM EN STATA: sacar una muestra y su media
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PROBABILITY INTERVALS VS CI (VERY IMPORTANT)
With age we cannot apply normal distribution, it is calculating a probability interval. We can only calculate the CI with a sample in ESTIMATORS.
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¿Qué observamos?
200 intervalos de confianza del 95% para la media de edad calculados en 200 muestras, cada una de 36 sujetos.
AL FINAL TENEMOS 5 CI WHICH FAIL, NO TOCAN LA REALIDAD, por ello 95% CI.
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PROBLEMA RESUELTO CON DISTRIBUCIÓN NORMAL Y BINOMIAL
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PROBLEMA A RESOLVER CON NORMAL Y POISSON
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Probability following a normal distribution
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SE
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T tail STATA
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Rejecting the null hypothesis
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Hypothesis testing for a proportion
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Hypothesis testing for a proportion in STATA
Always look at 2-tailed
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Hypothesis testing for a mean
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INTERPRETACIÓN p value
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Two-sample test of proportions in STATA
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Z test for proportions in STATA
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Chi 2 en STATA
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Getting expected values in STATA
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If expected values in chi are lower than 5, what do we use?
FISHER EXACT TEST
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Pearson chi 2 with rows and columns
Here we have 3 DF.
En la última foto, a la izquierda sacamos expected values y a la derecha observed
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Chi 2 y z with only one variable and many categories
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Mc Neman paired test for proportions
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Chi2 for linear trend
1df, ordinal variables
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T test parametric indecent variables STATA
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corregir CI en t-test
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F distribution para comparar SD, si es mayor que 0.05 cumple homogeneidad.
Mirar t-tail más pequeña
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Sd test con calculadora en STATA
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T test heterogeneous variances STATA
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Paired T-test en STATA
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Paired t test but with mean vs external reference
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ESQUEMA COMPARISON OF MEANS
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Mann Whitney U test STATA
