# R-help to Exercise 3

 

# Read the data into R and look at the data:

speed=scan("http://www.uio.no/studier/emner/matnat/math/STK4900/v17/exer2.dat")

speed

 

 

# QUESTION a)

 

# Plot the data in various ways:

hist(speed)                    # histogram

plot(ecdf(speed))            #empirical distribution function

boxplot(speed)             # box plot

 

# What do the different plots tell you?

# Are there indications for "outliers" in the data?

 

 

# QUESTION b)

 

# Compute the (empirical) mean and the median, which are the two most common measures of location

# (alternatively you may use the command summary(speed) to compute the mean and the median)

mean(speed)                 #mean

median(speed)              #median

 

# What do the two measures of location tell you?

 

 

# QUESTION c)

 

# Compute the (empirical) standard deviation and the interquartile range, which are two common measures of spread:

sd(speed)                     # standard deviation

IQR(speed)                  # interquartile range

 

# What do the two measures of spread tell you?

 

 

# QUESTION d)

 

# Compute t-based confidence interval using all data:

t.test(speed)

 

# Compute t-based confidence interval without the two "outliers":

t.test(speed[speed>0])

 

 

# What do the two intervals tell you? Which one do you find most reasonable?