install.packages("fEcofin", repos="http://R-Forge.R-project.org")

## Installing package into 'C:/Users/HP/Documents/R/win-library/3.6'
## (as 'lib' is unspecified)

## installing the source package 'fEcofin'

library(dplyr)

## 
## Attaching package: 'dplyr'

## The following objects are masked from 'package:stats':
## 
##     filter, lag

## The following objects are masked from 'package:base':
## 
##     intersect, setdiff, setequal, union

library(fEcofin)

library(tidyverse)

## -- Attaching packages ---- tidyverse 1.3.0 --

## v ggplot2 3.3.0     v purrr   0.3.3
## v tibble  2.1.3     v stringr 1.4.0
## v tidyr   1.0.0     v forcats 0.4.0
## v readr   1.3.1

## -- Conflicts ------- tidyverse_conflicts() --
## x dplyr::filter() masks stats::filter()
## x dplyr::lag()    masks stats::lag()

library(tidyr)

str(ford.s)

## 'data.frame':    2000 obs. of  2 variables:
##  $ X.m..d..y: Factor w/ 2000 levels "1/10/1985","1/10/1986",..: 716 774 790 797 803 809 666 682 689 695 ...
##  $ FORD     : num  0.02524 -0.03692 -0.01597 -0.00649 -0.01307 ...

# a

mean <- mean(ford.s$FORD)

mean

## [1] 0.0007600789

med <- median(ford.s$FORD)

med

## [1] 0

sd <- sd(ford.s$FORD)

sd

## [1] 0.01831557

# b

library(ggpubr)

## Loading required package: magrittr

## 
## Attaching package: 'magrittr'

## The following object is masked from 'package:purrr':
## 
##     set_names

## The following object is masked from 'package:tidyr':
## 
##     extract

ggdensity(ford.s$FORD,
          main = "Density plot tooth lenght",
          xlab = "Tooth length")

ggqqplot(ford.s$FORD)

# c

shapiro.test(ford.s$FORD)

## 
##  Shapiro-Wilk normality test
## 
## data:  ford.s$FORD
## W = 0.96388, p-value < 2.2e-16

# d

library(ggplot2)

qqnorm(ford.s$FORD)

qqplot(rt(ford.s$FORD, df = 1),ford.s$FORD, 
       main = "t(1) QQ plot",
       ylab = "Sample Quantiles")

qqplot(rt(ford.s$FORD, df = 2),ford.s$FORD,  
       main = "t(2) QQ plot",
       ylab = "Sample Quantiles")

qqplot(rt(ford.s$FORD, df = 3),ford.s$FORD, 
       main = "t(3) QQ plot",
       ylab = "Sample Quantiles")