var_test
performs tests on the equality of standard
deviations (variances).
var_test_shiny(data, variable1, variable2, alternative = c("less", "greater", "all"))
data | a dataframe |
---|---|
variable1 | character; name of sample 1 in data frame |
variable2 | character; name of sample 2 in data frame |
alternative | a character string specifying the alternative hypothesis, must be one of "both" (default), "greater", "less" or "all". You can specify just the initial letter. |
var_test
returns an object of class "var_test"
.
An object of class "var_test"
is a list containing the
following components:
f statistic
lower one-sided p-value
upper one-sided p-value
two-sided p-value
variances for each level of the grouping variable
means for each level of the grouping variable
standard deviations for each level of the grouping variable
standard errors for each level of the grouping variable
combined mean
combined standard deviation
estimated combined standard error
numerator degrees of freedom
denominator degrees of freedom
number of observations for each level of grouping variable
number of observations
levels of the grouping variable
alternative hypothesis
Sheskin, D. J. 2007. Handbook of Parametric and Nonparametric Statistical Procedures, 4th edition. : Chapman & Hall/CRC.
# using two variables # lower tail var_test_shiny(hsb, 'read', 'write', alternative = 'less')#> Variance Ratio Test #> -------------------------------------------------- #> Group Obs Mean Std. Err. Std. Dev. #> -------------------------------------------------- #> read 200 52.23 0.72 10.25 #> write 200 52.77 0.67 9.48 #> -------------------------------------------------- #> combined 400 52.5 0.49 9.86 #> -------------------------------------------------- #> #> Lower Tail Test #> --------------- #> ratio = sd(read) / (write) #> Ho: ratio = 1 #> Ha: ratio < 1 #> #> Variance Ratio Test #> ------------------------------------ #> F Num DF Den DF p #> ------------------------------------ #> 1.1701 199 199 0.8656 #> ------------------------------------# upper tail var_test_shiny(hsb, 'read', 'write', alternative = 'greater')#> Variance Ratio Test #> -------------------------------------------------- #> Group Obs Mean Std. Err. Std. Dev. #> -------------------------------------------------- #> read 200 52.23 0.72 10.25 #> write 200 52.77 0.67 9.48 #> -------------------------------------------------- #> combined 400 52.5 0.49 9.86 #> -------------------------------------------------- #> #> Upper Tail Test #> --------------- #> Ho: ratio = 1 #> Ha: ratio > 1 #> #> Variance Ratio Test #> ------------------------------------ #> F Num DF Den DF p #> ------------------------------------ #> 1.1701 199 199 0.1344 #> ------------------------------------# all tails var_test_shiny(hsb, 'read', 'write', alternative = 'all')#> Variance Ratio Test #> -------------------------------------------------- #> Group Obs Mean Std. Err. Std. Dev. #> -------------------------------------------------- #> read 200 52.23 0.72 10.25 #> write 200 52.77 0.67 9.48 #> -------------------------------------------------- #> combined 400 52.5 0.49 9.86 #> -------------------------------------------------- #> #> Variance Ratio Test #> -------------------------------------------------- #> F Num DF Den DF #> -------------------------------------------------- #> 1.1701 199 199 #> -------------------------------------------------- #> #> Null & Alternate Hypothesis #> ---------------------------------------- #> ratio = sd(read) / (write) #> Ho: ratio = 1 #> #> Ha: ratio < 1 Ha: ratio > 1 #> Pr(F < f) = 0.8656 Pr(F > f) = 0.1344 #> ----------------------------------------