Multiple Regression - Part 2

YouTube “Multiple Regression” videos

Route Delivery Schedule is as followed:

rds <- data.frame(miles=c(89,66,78,111,44,77,80,66,109,76),
                  numDelivers=c(4,1,3,6,1,3,3,2,5,3),
                  gasPrice=c(3.84,3.19,3.78,3.89,3.57,3.57,3.03,3.51,3.54,3.25),
                  travelTime=c(7,5.4,6.6,7.4,4.8,6.4,7,5.6,7.3,6.4))
rds  

##    miles numDelivers gasPrice travelTime
## 1     89           4     3.84        7.0
## 2     66           1     3.19        5.4
## 3     78           3     3.78        6.6
## 4    111           6     3.89        7.4
## 5     44           1     3.57        4.8
## 6     77           3     3.57        6.4
## 7     80           3     3.03        7.0
## 8     66           2     3.51        5.6
## 9    109           5     3.54        7.3
## 10    76           3     3.25        6.4

Independent variables are:

• miles - miles driven
• numDelivers - number of deliveries made
• gasPrice - gas price

Dependent variable is:

• travelTime - travel time in hours

Scatterplots of IV’s vs DV

attach(rds)
par(mfrow=c(1,3))
plot(miles, travelTime)
abline(lm(travelTime ~ miles))
plot(numDelivers, travelTime)
abline(lm(travelTime ~ numDelivers))
plot(gasPrice, travelTime)
abline(lm(travelTime ~ gasPrice))

Scatterplots of IV’s vs IV’s

pairs(~ miles + numDelivers + gasPrice, data=rds)

Correlation Analysis between variables

library(psych)

## Warning: package 'psych' was built under R version 3.1.3

corr.test(rds)

## Call:corr.test(x = rds)
## Correlation matrix 
##             miles numDelivers gasPrice travelTime
## miles        1.00        0.96     0.36       0.93
## numDelivers  0.96        1.00     0.50       0.92
## gasPrice     0.36        0.50     1.00       0.27
## travelTime   0.93        0.92     0.27       1.00
## Sample Size 
## [1] 10
## Probability values (Entries above the diagonal are adjusted for multiple tests.) 
##             miles numDelivers gasPrice travelTime
## miles        0.00        0.00     0.63       0.00
## numDelivers  0.00        0.00     0.43       0.00
## gasPrice     0.31        0.14     0.00       0.63
## travelTime   0.00        0.00     0.46       0.00
## 
##  To see confidence intervals of the correlations, print with the short=FALSE option