Exploratory Analysis of Motor Trend Car Data

Introduction

This report presents an exploratory data analysis of the built-in R dataset mtcars, which contains technical specifications of 32 automobiles.

The goal is to: - Understand the structure of the data - Produce summary statistics - Explore relationships between key variables

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Data Description

The dataset includes the following variables:

• mpg: Miles per gallon
• cyl: Number of cylinders
• disp: Engine displacement
• hp: Gross horsepower
• wt: Weight (1000 lbs)
• am: Transmission type (0 = automatic, 1 = manual)

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Load and Inspect Data

# Load dataset
data(mtcars)

# Display first rows
head(mtcars)

##                    mpg cyl disp  hp drat    wt  qsec vs am gear carb
## Mazda RX4         21.0   6  160 110 3.90 2.620 16.46  0  1    4    4
## Mazda RX4 Wag     21.0   6  160 110 3.90 2.875 17.02  0  1    4    4
## Datsun 710        22.8   4  108  93 3.85 2.320 18.61  1  1    4    1
## Hornet 4 Drive    21.4   6  258 110 3.08 3.215 19.44  1  0    3    1
## Hornet Sportabout 18.7   8  360 175 3.15 3.440 17.02  0  0    3    2
## Valiant           18.1   6  225 105 2.76 3.460 20.22  1  0    3    1

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Summary Statistics

summary(mtcars)

##       mpg             cyl             disp             hp       
##  Min.   :10.40   Min.   :4.000   Min.   : 71.1   Min.   : 52.0  
##  1st Qu.:15.43   1st Qu.:4.000   1st Qu.:120.8   1st Qu.: 96.5  
##  Median :19.20   Median :6.000   Median :196.3   Median :123.0  
##  Mean   :20.09   Mean   :6.188   Mean   :230.7   Mean   :146.7  
##  3rd Qu.:22.80   3rd Qu.:8.000   3rd Qu.:326.0   3rd Qu.:180.0  
##  Max.   :33.90   Max.   :8.000   Max.   :472.0   Max.   :335.0  
##       drat             wt             qsec             vs        
##  Min.   :2.760   Min.   :1.513   Min.   :14.50   Min.   :0.0000  
##  1st Qu.:3.080   1st Qu.:2.581   1st Qu.:16.89   1st Qu.:0.0000  
##  Median :3.695   Median :3.325   Median :17.71   Median :0.0000  
##  Mean   :3.597   Mean   :3.217   Mean   :17.85   Mean   :0.4375  
##  3rd Qu.:3.920   3rd Qu.:3.610   3rd Qu.:18.90   3rd Qu.:1.0000  
##  Max.   :4.930   Max.   :5.424   Max.   :22.90   Max.   :1.0000  
##        am              gear            carb      
##  Min.   :0.0000   Min.   :3.000   Min.   :1.000  
##  1st Qu.:0.0000   1st Qu.:3.000   1st Qu.:2.000  
##  Median :0.0000   Median :4.000   Median :2.000  
##  Mean   :0.4062   Mean   :3.688   Mean   :2.812  
##  3rd Qu.:1.0000   3rd Qu.:4.000   3rd Qu.:4.000  
##  Max.   :1.0000   Max.   :5.000   Max.   :8.000

The summary shows that fuel efficiency varies substantially across vehicles, with mileage ranging from low-performance to highly efficient cars.

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Relationship Between Weight and Fuel Efficiency

We investigate whether heavier cars consume more fuel.

plot(
  mtcars$wt,
  mtcars$mpg,
  xlab = "Weight (1000 lbs)",
  ylab = "Miles per Gallon",
  main = "Fuel Efficiency vs Car Weight"
)

abline(
  lm(mpg ~ wt, data = mtcars),
  col = "red"
)

The negative slope indicates that heavier cars tend to have lower fuel efficiency.

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Transmission Type Comparison

aggregate(mpg ~ am, data = mtcars, mean)

##   am      mpg
## 1  0 17.14737
## 2  1 24.39231

On average, manual transmission vehicles have higher fuel efficiency.

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Conclusion

This analysis shows that:

• Car weight strongly influences fuel efficiency
• Transmission type is associated with mileage differences
• R Markdown enables fully reproducible reporting

Future work could include regression modeling or interactive exploration using Shiny applications.

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