Team 3 - Aderinsola Sola, Vanessa Cecchini, Robert Hoffman, Fausat Ismail

Set up working directory

getwd()
## [1] "/Users/user/Desktop/Rstudio Work"
setwd("/Users/user/Desktop/Rstudio Work")

Load necessary libraries

library(ggplot2)
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(stringr)
library(visreg)
library(car)
## Loading required package: carData
## 
## Attaching package: 'car'
## The following object is masked from 'package:dplyr':
## 
##     recode

Read Data file Car_Total

Car_Total<-read.csv("/Users/user/Car_Total.csv")
names(Car_Total) 
##  [1] "X.1"          "Resp"         "Att_1"        "Att_2"        "Enj_1"       
##  [6] "Enj_2"        "Perform_1"    "Perform_2"    "Perform_3"    "WOM_1"       
## [11] "WOM_2"        "Futu_Pur_1"   "Futu_Pur_2"   "Valu_Percp_1" "Valu_Percp_2"
## [16] "Pur_Proces_1" "Pur_Proces_2" "Residence"    "Pay_Meth"     "Insur_Type"  
## [21] "Gender"       "Age"          "Education"    "X"            "Region"      
## [26] "Model"        "MPG"          "Cyl"          "acc1"         "C_cost."     
## [31] "H_Cost"       "Post.Satis"   "Att_Mean"     "Make"         "Model_v1"    
## [36] "Parent"
ct<-Car_Total  

Step 1

Choose the target car brand for statistical analyses

select the subset data on the target brand Dodge

stringr::str_detect(ct$Model, "Dodge") # Select the text values wiht "Dodge" 
##    [1] FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE
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## [1033] FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE
## [1045] FALSE FALSE FALSE FALSE FALSE
ct[str_detect(ct$Model, "Dodge"),] #just see data frame 
##     X.1   Resp Att_1 Att_2 Enj_1 Enj_2 Perform_1 Perform_2 Perform_3 WOM_1
## 196 196  Res23     7     7     7     6         6         6         2     6
## 207 207  Res24     6     6     6     5         5         6         3     4
## 218 218  Res25     7     7     7     5         5         7         2     7
## 229 229  Res26     2     3     3     2         2         4         5     5
## 240 240  Res27     7     7     7     6         6         6         6     6
## 251 251  Res28     2     2     2     2         2         2         2     2
## 262 262  Res29     5     5     5     4         4         5         5     4
## 274 274  Res30     5     3     3     2         2         3         4     3
## 285 285  Res31     7     7     7     6         6         6         5     4
## 296 296  Res32     7     7     7     6         6         6         2     6
## 307 307  Res33     4     2     3     2         2         3         2     6
## 318 318  Res34     6     6     7     4         5         6         6     4
## 329 329  Res35     5     5     5     5         5         1         1     7
## 340 340  Res36     6     6     5     5         5         5         1     6
## 351 351  Res37     2     2     2     2         2         2         2     2
## 362 362  Res38     6     6     6     5         5         6         2     5
## 373 373  Res39     6     6     6     5         5         5         5     4
## 385 385  Res40     1     1     1     1         1         1         1     1
## 396 396  Res41     1     1     1     1         1        NA         1     1
## 543 543 Res542     6     6     6     5         5         4         4     3
## 544 544 Res543     2     1     1     1         1         2         1     4
## 545 545 Res544     3     4     4     3         2         3         2     4
## 546 546 Res545     1     1     2     1         2         2         1     2
## 547 547 Res546     4     4     3     4         4         4         4     4
## 548 548 Res547     2     2     2     2         1         5         5     4
## 549 549 Res548     1     1     1     2         2         4         2     1
## 550 550 Res549     2     2     2     1         1         1         1     1
## 552 552 Res550     6     6     2     4         4         4         4     5
## 553 553 Res551     2     1     1     2         3         3         3     5
## 554 554 Res552     5     5     5     5         5         3         4     2
## 555 555 Res553     6     6     6     4         4         4         4     5
## 556 556 Res554     7     7     7     6         6         2         4     5
## 557 557 Res555     6     6     6     5         5         5         2     5
## 558 558 Res556     7     7     6     6         7         6         7     7
## 559 559 Res557     7     7     7     7         6         3         6     7
## 560 560 Res558     6     6     6     5         5         2         2     2
## 561 561 Res559     6     4     5     5         3         2         4     5
## 563 563 Res560     6     7     7     2         5         5         5     5
## 587 587 Res582     5     6     6     5         5         5         5     7
## 588 588 Res583     3     3     4     3         4         3         4     7
## 589 589 Res584     6     4     3     2         2         5         2     7
##     WOM_2 Futu_Pur_1 Futu_Pur_2 Valu_Percp_1 Valu_Percp_2 Pur_Proces_1
## 196     6          3          6            4            3            2
## 207     4          2          2            6            3            3
## 218     6          3          3            5            5            6
## 229     5          2          2            4            7            7
## 240     5          4          4            5            4            5
## 251     2          2          2            7            7            7
## 262     4          5          7            4            7            7
## 274     3          6          5            6            6            6
## 285     2          4          5            4            4            4
## 296     6          5          4            5            4            4
## 307     6          3          3            5            6            6
## 318     5          3          3            3            5            4
## 329     7          3          3            6            1            5
## 340     2          3          3            6            3            4
## 351     2          2          2            2            2            2
## 362     6          5          5            4            5            5
## 373     4          3          3            6            4            4
## 385     1          1          2            2            2            2
## 396     1          3          3            2            2            2
## 543     4          6          6            6            6            6
## 544     6          3          3            6            6            6
## 545     6          7          7            7            6            6
## 546     4          7          6            6            7            7
## 547     4          5          5            5            3            3
## 548     4          4          4            6            7            7
## 549     2          6          6            6            5            5
## 550     1          6          6            6            6            6
## 552     6          6          6            6            5            5
## 553     3          6          6            6            5            5
## 554     5          6          6            6            4            5
## 555     6          5          5            5            5            4
## 556     5          5          5            5            5            5
## 557     5          7          7            6            6            6
## 558     6          6          6            6            6            6
## 559     7          5          5            6            7            6
## 560     6          4          4            4            4            4
## 561     4          3          3            6            7            7
## 563     6          5          5            5            5            5
## 587     5          6          5            6            6            6
## 588     6          6          6            6            6            6
## 589     6          6          6            6            5            5
##     Pur_Proces_2 Residence Pay_Meth    Insur_Type Gender Age Education  X
## 196            4         2        2 Comprehensive   Male  26         2 NA
## 207            6         2        1               Female  26         3 NA
## 218            4         1        2 Comprehensive   Male  27         3 NA
## 229            7         2        1 Comprehensive Female  27         2 NA
## 240            5         2        1 Comprehensive   Male  27         2 NA
## 251            3         1        2 Comprehensive   Male  29         1 NA
## 262            2         2        1 Comprehensive   Male  32         2 NA
## 274            6         1        2 Comprehensive   Male  32         2 NA
## 285            4         1        2 Comprehensive   Male  32         2 NA
## 296            4         2        1 Comprehensive   Male  32         2 NA
## 307            6         1        2     Collision   Male  34         2 NA
## 318            4         1        2     Collision   Male  34         1 NA
## 329            1         2        1               Female  34         1 NA
## 340            4         1        2     Collision   Male  34         3 NA
## 351            6         2        2     Collision   Male  35         2 NA
## 362            4         1        2     Collision   Male  35         2 NA
## 373            5         2        1     Collision   Male  36         2 NA
## 385            5         2        1     Collision   Male  36         2 NA
## 396            5         2        2     Collision   Male  36         2 NA
## 543            6         1        1 Comprehensive Female  49         3 NA
## 544            6         2        3 Comprehensive   Male  49         2 NA
## 545            6         2        1 Comprehensive Female  50         2 NA
## 546            4         2        2 Comprehensive   Male  52         2 NA
## 547            4         1        1 Comprehensive Female  53         2 NA
## 548            7         1        1 Comprehensive   Male  53         1 NA
## 549            4         2        3 Comprehensive   Male  53         2 NA
## 550            6         2        1 Comprehensive   Male  54         2 NA
## 552            6         2        3 Comprehensive   Male  55         2 NA
## 553            5         2        2 Comprehensive   Male  55         1 NA
## 554            6         2        3 Comprehensive   Male  55         2 NA
## 555            6         2        2 Comprehensive   Male  56         2 NA
## 556            5         1        3 Comprehensive   Male  57         2 NA
## 557            7         1        2     Collision Female  57         2 NA
## 558            6         1        2     Collision   Male  57         2 NA
## 559            3         2        2     Collision   Male  57         2 NA
## 560            4         1        3     Collision   Male  60         2 NA
## 561            6         2        2     Collision   Male  60         2 NA
## 563            5         2        2     Collision   Male  18         2 NA
## 587            6         2        1 Comprehensive Female  25         1 NA
## 588            5         1        1 Comprehensive   Male  26         2 NA
## 589            5         2        1 Comprehensive   Male  26         2 NA
##             Region         Model MPG Cyl acc1 C_cost. H_Cost Post.Satis
## 196       American Dodge Journey  16   6 5.75      12     11          5
## 207       American Dodge Journey  16   6 5.75      12     11          4
## 218       American Dodge Journey  16   6 5.75      12     11          4
## 229       American Dodge Journey  16   6 5.75      12     11          5
## 240       American Dodge Journey  16   6 5.75      12     11          4
## 251       American Dodge Journey  16   6 5.75      12     11          3
## 262       American Dodge Journey  16   6 5.75      12     11          6
## 274       American Dodge Journey  16   6 5.75      12     11          5
## 285       American Dodge Journey  16   6 5.75      12     11          5
## 296       American Dodge Journey  16   6 5.75      12     11          4
## 307       American Dodge Journey  16   6 5.75      12     11          5
## 318       American Dodge Journey  16   6 5.75      12     11          5
## 329       American Dodge Journey  16   6 5.75      12     11          6
## 340       American Dodge Journey  16   6 5.75      12     11          4
## 351       American Dodge Journey  16   6 5.75      12     11          4
## 362       American Dodge Journey  16   6 5.75      12     11          3
## 373       American Dodge Journey  16   6 5.75      12     11          4
## 385       American Dodge Journey  16   6 5.75      12     11          3
## 396       American Dodge Journey  16   6 5.75      12     11          4
## 543 Middle Eastern Dodge Journey  16   6 5.75      12     11          6
## 544 Middle Eastern Dodge Journey  16   6 5.75      12     11          3
## 545 Middle Eastern Dodge Journey  16   6 5.75      12     11          4
## 546 Middle Eastern Dodge Journey  16   6 5.75      12     11          4
## 547 Middle Eastern Dodge Journey  16   6 5.75      12     11          3
## 548 Middle Eastern Dodge Journey  16   6 5.75      12     11          3
## 549 Middle Eastern Dodge Journey  16   6 5.75      12     11          6
## 550 Middle Eastern Dodge Journey  16   6 5.75      12     11          7
## 552 Middle Eastern Dodge Journey  16   6 5.75      12     11          3
## 553 Middle Eastern Dodge Journey  16   6 5.75      12     11          6
## 554 Middle Eastern Dodge Journey  16   6 5.75      12     11          7
## 555 Middle Eastern Dodge Journey  16   6 5.75      12     11          6
## 556 Middle Eastern Dodge Journey  16   6 5.75      12     11          5
## 557 Middle Eastern Dodge Journey  16   6 5.75      12     11          3
## 558 Middle Eastern Dodge Journey  16   6 5.75      12     11          5
## 559 Middle Eastern Dodge Journey  16   6 5.75      12     11          5
## 560 Middle Eastern Dodge Journey  16   6 5.75      12     11          3
## 561 Middle Eastern Dodge Journey  16   6 5.75      12     11          5
## 563 Middle Eastern Dodge Journey  16   6 5.75      12     11          6
## 587       American Dodge Journey  16   6 5.75      12     11          6
## 588       American Dodge Journey  16   6 5.75      12     11          5
## 589       American Dodge Journey  16   6 5.75      12     11          6
##     Att_Mean  Make Model_v1   Parent
## 196      7.0 Dodge  Journey Chrysler
## 207      6.0 Dodge  Journey Chrysler
## 218      7.0 Dodge  Journey Chrysler
## 229      2.5 Dodge  Journey Chrysler
## 240      7.0 Dodge  Journey Chrysler
## 251      2.0 Dodge  Journey Chrysler
## 262      5.0 Dodge  Journey Chrysler
## 274      4.0 Dodge  Journey Chrysler
## 285      7.0 Dodge  Journey Chrysler
## 296      7.0 Dodge  Journey Chrysler
## 307      3.0 Dodge  Journey Chrysler
## 318      6.0 Dodge  Journey Chrysler
## 329      5.0 Dodge  Journey Chrysler
## 340      6.0 Dodge  Journey Chrysler
## 351      2.0 Dodge  Journey Chrysler
## 362      6.0 Dodge  Journey Chrysler
## 373      6.0 Dodge  Journey Chrysler
## 385      1.0 Dodge  Journey Chrysler
## 396      1.0 Dodge  Journey Chrysler
## 543      6.0 Dodge  Journey Chrysler
## 544      1.5 Dodge  Journey Chrysler
## 545      3.5 Dodge  Journey Chrysler
## 546      1.0 Dodge  Journey Chrysler
## 547      4.0 Dodge  Journey Chrysler
## 548      2.0 Dodge  Journey Chrysler
## 549      1.0 Dodge  Journey Chrysler
## 550      2.0 Dodge  Journey Chrysler
## 552      6.0 Dodge  Journey Chrysler
## 553      1.5 Dodge  Journey Chrysler
## 554      5.0 Dodge  Journey Chrysler
## 555      6.0 Dodge  Journey Chrysler
## 556      7.0 Dodge  Journey Chrysler
## 557      6.0 Dodge  Journey Chrysler
## 558      7.0 Dodge  Journey Chrysler
## 559      7.0 Dodge  Journey Chrysler
## 560      6.0 Dodge  Journey Chrysler
## 561      5.0 Dodge  Journey Chrysler
## 563      6.5 Dodge  Journey Chrysler
## 587      5.5 Dodge  Journey Chrysler
## 588      3.0 Dodge  Journey Chrysler
## 589      5.0 Dodge  Journey Chrysler
ct_Dodge<-str_detect(ct$Model, "Dodge") #assign into a new data frame 
ct_Dodge #See new data frame 
##    [1] FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE
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##  [949] FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE
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##  [997] FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE
## [1009] FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE
## [1021] FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE
## [1033] FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE
## [1045] FALSE FALSE FALSE FALSE FALSE
subdodge<-ct[ct_Dodge,] ## assign subset data into a data frame 

table(subdodge$Make) ## double check on the models selected 
## 
## Dodge 
##    41

Divide age categories

subdodge$AgeGrp<-cut(subdodge$Age,
                      breaks = c(0, 40, Inf),
                      Labels = c("Young Adults", "Matured Adults"),
                      right=FALSE)
names(subdodge)
##  [1] "X.1"          "Resp"         "Att_1"        "Att_2"        "Enj_1"       
##  [6] "Enj_2"        "Perform_1"    "Perform_2"    "Perform_3"    "WOM_1"       
## [11] "WOM_2"        "Futu_Pur_1"   "Futu_Pur_2"   "Valu_Percp_1" "Valu_Percp_2"
## [16] "Pur_Proces_1" "Pur_Proces_2" "Residence"    "Pay_Meth"     "Insur_Type"  
## [21] "Gender"       "Age"          "Education"    "X"            "Region"      
## [26] "Model"        "MPG"          "Cyl"          "acc1"         "C_cost."     
## [31] "H_Cost"       "Post.Satis"   "Att_Mean"     "Make"         "Model_v1"    
## [36] "Parent"       "AgeGrp"
head(subdodge$AgeGrp)
## [1] [0,40) [0,40) [0,40) [0,40) [0,40) [0,40)
## Levels: [0,40) [40,Inf)

Independent sample t-test (Age Group by Post Purchase Satisfaction)

boxplot(subdodge$Post.Satis ~ subdodge$AgeGrp, col=c(5,7)) #visually check normality of residuals 

shapiro.test(subdodge$Post.Satis) #Pvalue < 0.05 means is significance 
## 
##  Shapiro-Wilk normality test
## 
## data:  subdodge$Post.Satis
## W = 0.90319, p-value = 0.002063
res_aov<-aov(Post.Satis ~ AgeGrp, data=subdodge)
res_aov
## Call:
##    aov(formula = Post.Satis ~ AgeGrp, data = subdodge)
## 
## Terms:
##                   AgeGrp Residuals
## Sum of Squares   0.03393  57.47826
## Deg. of Freedom        1        39
## 
## Residual standard error: 1.214002
## Estimated effects may be unbalanced

Histogram

hist(res_aov$residuals)

#### Create QQ Plot (visually check normaliity of the data)

qqnorm(res_aov$residuals, pch=1, frame=FALSE)
qqline(res_aov$residuals, col="blue", lwd=4)

#### Test normality of the residuals

shapiro.test(res_aov$residuals)
## 
##  Shapiro-Wilk normality test
## 
## data:  res_aov$residuals
## W = 0.91142, p-value = 0.003668

Barlett test of homogeneity of variances

bartlett.test(subdodge$Post.Satis, subdodge$AgeGrp)
## 
##  Bartlett test of homogeneity of variances
## 
## data:  subdodge$Post.Satis and subdodge$AgeGrp
## Bartlett's K-squared = 2.8247, df = 1, p-value = 0.09282

Research Question:

  • Null Hypothesis (H₀): There is no difference in the mean Post Purchase satisfaction scores between the two age groups ([0,40) and [40,Inf)).
  • Alternative Hypothesis (H₁): There is a difference in the mean Post purchase satisfaction scores between the two age group
t.test(Post.Satis~AgeGrp, data=subdodge, var.eq=TRUE)
## 
##  Two Sample t-test
## 
## data:  Post.Satis by AgeGrp
## t = -0.15174, df = 39, p-value = 0.8802
## alternative hypothesis: true difference in means between group [0,40) and group [40,Inf) is not equal to 0
## 95 percent confidence interval:
##  -0.8307242  0.7147821
## sample estimates:
##   mean in group [0,40) mean in group [40,Inf) 
##               4.608696               4.666667

One way anova

Independent variable: Age Grp

Dependent variable: Perform_1

  • H0: There is no significant difference for the usefulness of the vehicle across Age Groups
  • H1 There is significant difference for the usefulness of the vehicle across Age Groups
tapply(subdodge$Perform_1,subdodge$AgeGrp,shapiro.test)
## $`[0,40)`
## 
##  Shapiro-Wilk normality test
## 
## data:  X[[i]]
## W = 0.82963, p-value = 0.001188
## 
## 
## $`[40,Inf)`
## 
##  Shapiro-Wilk normality test
## 
## data:  X[[i]]
## W = 0.93601, p-value = 0.2473

Check homogeneity

bartlett.test(subdodge$Perform_1, subdodge$AgeGrp) #Bartlett test of homogeneity of variances 
## 
##  Bartlett test of homogeneity of variances
## 
## data:  subdodge$Perform_1 and subdodge$AgeGrp
## Bartlett's K-squared = 0.10308, df = 1, p-value = 0.7482

ANOVA

aov_perform_equal <- aov(Perform_1 ~ as.factor(AgeGrp), var.equal = FALSE, data=subdodge)
## Warning: In lm.fit(x, y, offset = offset, singular.ok = singular.ok, ...) :
##  extra argument 'var.equal' will be disregarded
summary(aov_perform_equal)
##                   Df Sum Sq Mean Sq F value Pr(>F)
## as.factor(AgeGrp)  1   0.85   0.848   0.261  0.613
## Residuals         39 126.96   3.255

#Pairwise t-tests With no assumption ot equal variances

pairwise.t.test(subdodge$Att_1, subdodge$AgeGrp, p.adjust.methods = "BH" , pool.sd = FALSE)
## 
##  Pairwise comparisons using t tests with non-pooled SD 
## 
## data:  subdodge$Att_1 and subdodge$AgeGrp 
## 
##          [0,40)
## [40,Inf) 0.48  
## 
## P value adjustment method: holm

Step 2

ggplot(subdodge,aes(x=Age, fill = Region,)) +
  theme_bw()+
  geom_bar()+
  geom_text(stat="count", aes(label=..count..), vjust=0) +
  labs(y="number of Participants",
       x = "Age",
       title ="Age")
## Warning: The dot-dot notation (`..count..`) was deprecated in ggplot2 3.4.0.
## ℹ Please use `after_stat(count)` instead.
## This warning is displayed once every 8 hours.
## Call `lifecycle::last_lifecycle_warnings()` to see where this warning was
## generated.

ggplot(subdodge,aes(x=Pay_Meth, fill = Region,)) +
  theme_bw()+
  geom_bar()+
  geom_text(stat="count", aes(label=..count..), vjust=0) +
  labs(y="number of Participants",
       x = "Payment Method",
       title ="Payment Method")

ggplot(subdodge,aes(x=Insur_Type, fill = Region,)) +
  theme_bw()+
  geom_bar()+
  geom_text(stat="count", aes(label=..count..), vjust=0) +
  labs(y="number of Participants",
       x = "Insur_Type",
       title ="Insur_Type")

## Step 3

data_lb<-subdodge

Multiple Linear Regression

model3<-lm(Age ~ Futu_Pur_1+Post.Satis+Enj_1, data = data_lb)
summary(model3)
## 
## Call:
## lm(formula = Age ~ Futu_Pur_1 + Post.Satis + Enj_1, data = data_lb)
## 
## Residuals:
##      Min       1Q   Median       3Q      Max 
## -20.5982  -7.0996  -0.6879   6.6725  25.6311 
## 
## Coefficients:
##             Estimate Std. Error t value Pr(>|t|)    
## (Intercept)  37.7874     8.3568   4.522 6.11e-05 ***
## Futu_Pur_1    3.7224     1.1985   3.106  0.00363 ** 
## Post.Satis   -1.8550     1.6449  -1.128  0.26671    
## Enj_1        -1.0621     0.8602  -1.235  0.22470    
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
## 
## Residual standard error: 11.66 on 37 degrees of freedom
## Multiple R-squared:  0.2343, Adjusted R-squared:  0.1722 
## F-statistic: 3.773 on 3 and 37 DF,  p-value: 0.01852

Visual inspection of Linearity

visreg(model3)

#### visualizing their relationships

ggplot(data_lb)+aes(x=Futu_Pur_1, y= Post.Satis, size = Enj_1)+
  geom_point()+ scale_color_gradient()+
  labs (y = "Future Purchase", x= "Post Purchase Satisfaction", color = "Enjoyment")+
  theme_minimal()

vif(model3) # check if variance inflation factor (vif) <10
## Futu_Pur_1 Post.Satis      Enj_1 
##   1.120217   1.143813   1.023011

Check linearity of residuels

plot(model3, which = 1)

#### Use a qq plot

plot(model3, which = 2)

#### Use shapiro-wilk test

shapiro.test(residuals(model3))
## 
##  Shapiro-Wilk normality test
## 
## data:  residuals(model3)
## W = 0.98162, p-value = 0.7366

Check HOmoscedacity (Contant Variance )

plot(model3, which=3)