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 |
Straight | 7 (50.00%) | 7 (50.00%) | ||
1/4 mile time | Mean | 18.2 | 17.4 | p value: 0.2057 |
6.2 Regression analysis
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 |