6 Statistical tests

6.1 Chi-square and t-Student’s test

tab3 <- crosstable(mtcars, c(vs, qsec), by=am, funs=mean, test=TRUE)
tab3 <- flextable(tab3, col_keys=c("label", "variable", "0", "1", "test"))
tab3 <- merge_v(tab3, j=c("label","test"))
tab3 <- mk_par(tab3, j=1, 
  value=as_paragraph(as_chunk("Variable")), part="header")
tab3 <- mk_par(tab3, j=2, 
  value=as_paragraph(as_chunk("Label")), part="header")
tab3 <- mk_par(tab3, j=3, 
  value=as_paragraph(as_chunk("Automatic")), part="header")
tab3 <- mk_par(tab3, j=4, 
  value=as_paragraph(as_chunk("Manual")), part="header")
names <- c("Engine","1/4 mile time")
tab3 <- mk_par(tab3, j=1, i=c(1,3), 
     value=as_paragraph(as_chunk(names)))
names <- c("V-shapped","Straight","Mean")
tab3 <- mk_par(tab3, j=2, i=1:3, 
     value=as_paragraph(as_chunk(names)))
tab3 <- add_header_row(tab3, values=c("","Transmission",""), colwidths=c(2,2,1))
tab3 <- hline(tab3, i=2, border=fp_border_default())
tab3 <- flextable::align(tab3, part="all", align="center")
tab3 <- width(tab3, width=2)
tab3

Transmission

Variable

Label

Automatic

Manual

test

Engine

V-shapped

12 (66.67%)

6 (33.33%)

p value: 0.3409
(Pearson's Chi-squared test)

Straight

7 (50.00%)

7 (50.00%)

1/4 mile time

Mean

18.2

17.4

p value: 0.2057
(Two Sample t-test)

6.2 Regression analysis

fit <- lm(mpg ~ wt + hp, data = mtcars)

# Convert to flextable
ft <- as_flextable(fit)
ft

Estimate

Standard Error

t value

Pr(>|t|)

(Intercept)

37.227

1.599

23.285

0.0000

***

wt

-3.878

0.633

-6.129

0.0000

***

hp

-0.032

0.009

-3.519

0.0015

**

Signif. codes: 0 <= '***' < 0.001 < '**' < 0.01 < '*' < 0.05

Residual standard error: 2.593 on 29 degrees of freedom

Multiple R-squared: 0.8268, Adjusted R-squared: 0.8148

F-statistic: 69.21 on 29 and 2 DF, p-value: 0.0000