Installation
Install R/CTTvis from Github using the devtools package
devtools::install_github("TaridWong/CTTvis")Or get the released version from CRAN
install.packages("CTTvis")Example use
library(CTTvis)To demonstrate thedifficulty_plot andpoint_biserial_plot functions, we will first load abuilt-in dataset calleddichotomous_response.
In some context, item difficulty flag thresholds may change. This canbe adjusted using theeasyFlag andhardFlagarguments. The following use the easy flag threshold of .8, meaning thatitems that gets answered correctly 80% of the total test takers orgreater are considered easy. On the other hand, items that gets answeredcorrectly 60% of the total test takers or less are considereddifficult.
data(dichotomous_response)difficulty_plot(responses = dichotomous_response,title ="Item Difficulty Plot",easyFlag = .80,hardFlag = .60)For thepoint_biserial_plot function, you could adjustyour point-biserial correlation (pBis) threshold as well. For example,if you want the pBis threshold to be .3, you could configure thepBis_threshold as follows:
point_biserial_plot(responses = dichotomous_response,title ="Item Discrimination Plot",pBis_threshold =0.30)To demonstrate thecoefficient_alpha_plot function, weneed to load another built-in dataset calledreliability_df. This dataset was simulated to test thecapability of this function.
The influence of an item when dropped to the overall unidimensionalcoefficient alpha could vary, hence the option to configure the roundingof overall coefficient alpha. For example, if dropping an item increasesthe overall coefficient alpha by 0.001, then rounding the alpha by threedecimal places could allow researchers to see the increase compared torounding the alpha by two decimal points.
The following demonstration rounds the overall alpha by four decimalpoints. This argument can be adjusted based on the researchers’needs.
data(reliability_df)coefficient_alpha_plot(responses = reliability_df,title ="Coefficient Alpha Plot",alpha_round =4)Licenses
The R/CTTvis package as a whole is distributed underGPL-3 (GNU GeneralPublic License version 3).
[8]ページ先頭