ind_ttest
compares the means of two independent groups in order to determine whether
there is statistical evidence that the associated population means are significantly different.
ind_ttest(data, x, y, confint = 0.95, alternative = c("both", "less", "greater", "all"), ...)
factor
numeric
vectorind_ttest
returns an object of class "ind_ttest"
.
An object of class "ind_ttest"
is a list containing the
following components:
Sheskin, D. J. 2007. Handbook of Parametric and Nonparametric Statistical Procedures, 4th edition. : Chapman & Hall/CRC.
# data hsb2 <- inferr::hsb hsb2$female <- as.factor(hsb2$female) # lower tail ind_ttest(hsb2, 'female', 'write', alternative = 'less')#> Group Statistics #> ----------------------------------------------------------------------------- #> Group Obs Mean Std. Err. Std. Dev. [95% Conf. Interval] #> ----------------------------------------------------------------------------- #> 0 91 50.121 1.080 10.305 47.975 52.267 #> 1 109 54.991 0.779 8.134 53.447 56.535 #> ----------------------------------------------------------------------------- #> combined 200 52.775 0.67 9.479 51.454 54.096 #> ----------------------------------------------------------------------------- #> diff 200 -4.87 1.304 9.231 -7.426 -2.314 #> ----------------------------------------------------------------------------- #> #> Independent Samples Test #> ------------------------ #> #> Ho: mean(0) - mean(1) = diff = 0 #> Ha: diff < 0 #> #> --------------------------------------------------------------------- #> Variable Method Variances DF t Value P < t #> --------------------------------------------------------------------- #> write Pooled Equal 198 -3.7347 0.0001 #> write Satterthwaite Unequal 170 -3.6564 0.0002 #> --------------------------------------------------------------------- #> #> Test for Equality of Variances #> --------------------------------------------------------------- #> Variable Method Num DF Den DF F Value P > F #> --------------------------------------------------------------- #> write Folded F 90 108 1.605 0.0188 #> ---------------------------------------------------------------# upper tail ind_ttest(hsb2, 'female', 'write', alternative = 'greater')#> Group Statistics #> ----------------------------------------------------------------------------- #> Group Obs Mean Std. Err. Std. Dev. [95% Conf. Interval] #> ----------------------------------------------------------------------------- #> 0 91 50.121 1.080 10.305 47.975 52.267 #> 1 109 54.991 0.779 8.134 53.447 56.535 #> ----------------------------------------------------------------------------- #> combined 200 52.775 0.67 9.479 51.454 54.096 #> ----------------------------------------------------------------------------- #> diff 200 -4.87 1.304 9.231 -7.426 -2.314 #> ----------------------------------------------------------------------------- #> #> Independent Samples Test #> ------------------------ #> #> Ho: mean(0) - mean(1) = diff = 0 #> Ha: diff > 0 #> #> --------------------------------------------------------------------- #> Variable Method Variances DF t Value P > t #> --------------------------------------------------------------------- #> write Pooled Equal 198 -3.7347 0.9999 #> write Satterthwaite Unequal 170 -3.6564 0.9998 #> --------------------------------------------------------------------- #> #> Test for Equality of Variances #> --------------------------------------------------------------- #> Variable Method Num DF Den DF F Value P > F #> --------------------------------------------------------------- #> write Folded F 90 108 1.605 0.0188 #> ---------------------------------------------------------------# both tails ind_ttest(hsb2, 'female', 'write', alternative = 'both')#> Group Statistics #> ----------------------------------------------------------------------------- #> Group Obs Mean Std. Err. Std. Dev. [95% Conf. Interval] #> ----------------------------------------------------------------------------- #> 0 91 50.121 1.080 10.305 47.975 52.267 #> 1 109 54.991 0.779 8.134 53.447 56.535 #> ----------------------------------------------------------------------------- #> combined 200 52.775 0.67 9.479 51.454 54.096 #> ----------------------------------------------------------------------------- #> diff 200 -4.87 1.304 9.231 -7.426 -2.314 #> ----------------------------------------------------------------------------- #> #> Independent Samples Test #> ------------------------ #> #> Ho: mean(0) - mean(1) = diff = 0 #> Ha: diff ~= 0 #> #> --------------------------------------------------------------------- #> Variable Method Variances DF t Value P > |t| #> --------------------------------------------------------------------- #> write Pooled Equal 198 -3.7347 0.0002 #> write Satterthwaite Unequal 170 -3.6564 0.0003 #> --------------------------------------------------------------------- #> #> Test for Equality of Variances #> --------------------------------------------------------------- #> Variable Method Num DF Den DF F Value P > F #> --------------------------------------------------------------- #> write Folded F 90 108 1.605 0.0188 #> ---------------------------------------------------------------# all tails ind_ttest(hsb2, 'female', 'write', alternative = 'all')#> Group Statistics #> ----------------------------------------------------------------------------- #> Group Obs Mean Std. Err. Std. Dev. [95% Conf. Interval] #> ----------------------------------------------------------------------------- #> 0 91 50.121 1.080 10.305 47.975 52.267 #> 1 109 54.991 0.779 8.134 53.447 56.535 #> ----------------------------------------------------------------------------- #> combined 200 52.775 0.67 9.479 51.454 54.096 #> ----------------------------------------------------------------------------- #> diff 200 -4.87 1.304 9.231 -7.426 -2.314 #> ----------------------------------------------------------------------------- #> #> Independent Samples Test #> ------------------------ #> #> Ho: mean(0) - mean(1) = diff = 0 #> #> Ha: diff < 0 Ha: diff ~= 0 Ha: diff > 0 #> #> Pooled #> ------------------------------------------------------------------------ #> t = -3.7347 t = -3.7347 t = -3.7347 #> P < t = 0.0001 P > |t| = 0.0002 P > t = 0.9999 #> #> Satterthwaite #> ------------------------------------------------------------------------ #> t = -3.6564 t = -3.6564 t = -3.6564 #> P < t = 0.0002 P > |t| = 0.0003 P > t = 0.9998 #> #> #> Test for Equality of Variances #> --------------------------------------------------------------- #> Variable Method Num DF Den DF F Value P > F #> --------------------------------------------------------------- #> write Folded F 90 108 1.605 0.0188 #> ---------------------------------------------------------------