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#ZADATAK 1. Komarci

#1
boxplot(komarci$beer, komarci$water, names=c("Pivo", "Voda"))

#2
hist(komarci$beer, breaks=10,
     main = "Histogram s normalnom krivuljom", xlab= "Pivo", ylab="Frekvencije")
curve(dnorm(x, mean = mean(komarci$beer), sd = sd(komarci$beer)), 
     lwd = 2, add = TRUE)

hist(komarci$water, breaks=10,
     main = "Histogram s normalnom krivuljom", xlab= "Voda", ylab="Frekvencije")
curve(dnorm(x, mean = mean(komarci$water, na.rm = TRUE), sd = sd(komarci$beer, na.rm = TRUE)), 
      lwd = 2, add = TRUE)
qqnorm(komarci$beer)
qqline(komarci$beer)
qqnorm(komarci$water)
qqline(komarci$water)

var.test(komarci$beer, komarci$water, alternative="two.sided")
#p-value = 0.317

#3
t.test(komarci$beer, komarci$water, alternative="two.sided", var.equal = TRUE)
#p-value = 0.001915




###########################################

#ZADATAK 2. Banke

#1
boxplot(banke$c, banke$d, names=c("Banka C", "Banka D"))

#2
hist(banke$c,
     main = "Histogram s normalnom krivuljom", xlab= "Banka C", ylab="Frekvencije")
curve(dnorm(x, mean = mean(banke$c), sd = sd(banke$c)), 
      lwd = 2, add = TRUE)
qqnorm(banke$c)
qqline(banke$c)

hist(banke$d, breaks = 10, freq = FALSE,
     main = "Histogram s normalnom krivuljom", xlab= "Banka D", ylab="Frekvencije")
curve(dnorm(x, mean = mean(banke$d, na.rm=TRUE), sd = sd(banke$d, na.rm=TRUE)), 
      lwd = 2, add = TRUE)
qqnorm(banke$d)
qqline(banke$d)

#3
var.test(banke$c, banke$d, alternative="two.sided")
#p-value = 0.317

#4
t.test(banke$c, banke$d, alternative="two.sided", var.equal = TRUE)



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#ZADATAK 3.


###########################################

#ZADATAK 4. Mortalitet
t.test(mortalitet$nizi_porez, mortalitet$visi_porez, paired = TRUE, alternative="two.sided")
#p-value = 0.08491



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#ZADATAK 6. Ribe
#Uočimo da su ovdje podaci za obe populacije u jednom stupcu!
#1
boxplot(ribe$preference ~ ribe$genotype, data=ribe)
#Očekujemo da F2 populacija ima veću varijancu

#2
var.test(x1$preference, x2$preference, alternative="two.sided")
#p-value = 0.0001266


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#ZADATAK 7. Normalnost

#Paket za skewness i kurtosis
install.packages("e1071")
library(e1071)

#Primjer za ribe
#2
x1<-subset(ribe, select="preference", ribe$genotype=="F1")
x1
hist(x1$preference, breaks=10,
     main = "Histogram s normalnom krivuljom", xlab= "F1", ylab="Frekvencije")
curve(dnorm(x, mean = mean(x1$preference), sd = sd(x1$preference)), 
      lwd = 2, add = TRUE)
qqnorm(x1$preference)
qqline(x1$preference)
skewness(x1$preference, type = 2)
# -0.06546237
kurtosis(x1$preference, type = 2)
# -0.8312478

x2<-subset(ribe, select="preference", ribe$genotype=="F2")
x2
hist(x2$preference, breaks=10,
     main = "Histogram s normalnom krivuljom", xlab= "F2", ylab="Frekvencije")
curve(dnorm(x, mean = mean(x2$preference), sd = sd(x2$preference)), 
      lwd = 2, add = TRUE)
qqnorm(x2$preference)
qqline(x2$preference)
skewness(x2$preference, type = 2)
# -0.130584
kurtosis(x2$preference, type = 2)
# 0.6963482


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