Inferencia

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Database<-read.csv("lbw.csv", sep = ",", dec = "." ) 
str(Database)

## 'data.frame':    189 obs. of  11 variables:
##  $ X    : int  1 2 3 4 5 6 7 8 9 10 ...
##  $ low  : int  0 0 0 0 0 0 0 0 0 0 ...
##  $ smoke: int  0 0 1 1 1 0 0 0 1 1 ...
##  $ race : int  2 3 1 1 1 3 1 3 1 1 ...
##  $ age  : int  19 33 20 21 18 21 22 17 29 26 ...
##  $ lwt  : int  182 155 105 108 107 124 118 103 123 113 ...
##  $ ptl  : int  0 0 0 0 0 0 0 0 0 0 ...
##  $ ht   : int  0 0 0 0 0 0 0 0 0 0 ...
##  $ ui   : int  1 0 0 1 1 0 0 0 0 0 ...
##  $ ftv  : int  0 3 1 2 0 0 1 1 1 0 ...
##  $ bwt  : int  2523 2551 2557 2594 2600 2622 2637 2637 2663 2665 ...

Database$low<-as.factor(Database$low)
Database$smoke<-as.factor(Database$smoke)
Database$race<-as.factor(Database$race)
Database$ht<-as.factor(Database$ht)
Database$ui<-as.factor(Database$ui)
##Datos que quieres convertir a Factor
str(Database)

## 'data.frame':    189 obs. of  11 variables:
##  $ X    : int  1 2 3 4 5 6 7 8 9 10 ...
##  $ low  : Factor w/ 2 levels "0","1": 1 1 1 1 1 1 1 1 1 1 ...
##  $ smoke: Factor w/ 2 levels "0","1": 1 1 2 2 2 1 1 1 2 2 ...
##  $ race : Factor w/ 3 levels "1","2","3": 2 3 1 1 1 3 1 3 1 1 ...
##  $ age  : int  19 33 20 21 18 21 22 17 29 26 ...
##  $ lwt  : int  182 155 105 108 107 124 118 103 123 113 ...
##  $ ptl  : int  0 0 0 0 0 0 0 0 0 0 ...
##  $ ht   : Factor w/ 2 levels "0","1": 1 1 1 1 1 1 1 1 1 1 ...
##  $ ui   : Factor w/ 2 levels "0","1": 2 1 1 2 2 1 1 1 1 1 ...
##  $ ftv  : int  0 3 1 2 0 0 1 1 1 0 ...
##  $ bwt  : int  2523 2551 2557 2594 2600 2622 2637 2637 2663 2665 ...

##estimar un intervalo de confianza del 95% para la media poblacion de la variable bwt

t.test(Database$bwt,conf.level = 0.95)

## 
##  One Sample t-test
## 
## data:  Database$bwt
## t = 55.523, df = 188, p-value < 2.2e-16
## alternative hypothesis: true mean is not equal to 0
## 95 percent confidence interval:
##  2839.679 3048.892
## sample estimates:
## mean of x 
##  2944.286