| IntervalQuestionStat-package | Tools to Deal with Interval-Valued Responses in Questionnaires | 
| *-method | Interval arithmetic operations | 
| +-method | Interval arithmetic operations | 
| --method | Interval arithmetic operations | 
| apply | Apply functions over 'IntervalMatrix' margins | 
| apply-method | Apply functions over 'IntervalMatrix' margins | 
| arithmetic | Interval arithmetic operations | 
| as.IntervalData | Convert a real number into a degenerate interval | 
| as.IntervalData-method | Convert a real number into a degenerate interval | 
| as.IntervalList | Convert a single interval to a list of intervals | 
| as.IntervalList-method | Convert a single interval to a list of intervals | 
| c | Combine 'IntervalData' and 'IntervalList' objects | 
| c-method | Combine 'IntervalData' and 'IntervalList' objects | 
| cbind | Combine 'IntervalList' and 'IntervalMatrix' objects by columns | 
| cbind-method | Combine 'IntervalList' and 'IntervalMatrix' objects by columns | 
| cov | Calculate the sample covariance between two random intervals | 
| cov-method | Calculate the sample covariance between two random intervals | 
| cronbach | Estimate sample Cronbach's alpha coefficient | 
| dim | Get the number of rows and columns of an 'IntervalMatrix' object | 
| dim-method | Get the number of rows and columns of an 'IntervalMatrix' object | 
| distance | Calculate the theta-distance between two intervals | 
| distance-method | Calculate the theta-distance between two intervals | 
| extract | Extract and replace parts of an interval-valued object | 
| IntervalData | Create an 'IntervalData' object | 
| IntervalData-class | S4 class representing a single interval | 
| IntervalDataOrIntervalList-class | Virtual union of 'IntervalData' and 'IntervalList' classes | 
| IntervalList | Create an 'IntervalList' object | 
| IntervalList-class | S4 class representing a list of intervals | 
| IntervalListOrIntervalMatrix-class | Virtual union of 'IntervalList' and 'IntervalMatrix' classes | 
| IntervalMatrix | Create an 'IntervalMatrix' object | 
| IntervalMatrix-class | S4 class representing a matrix of intervals | 
| ivs2likert | Convert interval-valued responses into their equivalent numerically encoded Likert-type scale answers with minimum theta-distance criterion | 
| ivs2likert-method | Convert interval-valued responses into their equivalent numerically encoded Likert-type scale answers with minimum theta-distance criterion | 
| ivs2vas | Convert interval-valued responses into equivalent visual analogue scale answers through mid-point criterion | 
| ivs2vas-method | Convert interval-valued responses into equivalent visual analogue scale answers through mid-point criterion | 
| lackinfo | Lack of information in expository face-to-face lessons data set | 
| length | Get the length of an 'IntervalList' object | 
| length-method | Get the length of an 'IntervalList' object | 
| mean | Calculate the sample Aumann mean of a random interval | 
| mean-method | Calculate the sample Aumann mean of a random interval | 
| mid | Extract and replace the mid-points of interval-valued objects | 
| mid-method | Extract and replace the mid-points of interval-valued objects | 
| mid<- | Extract and replace the mid-points of interval-valued objects | 
| mid<--method | Extract and replace the mid-points of interval-valued objects | 
| ncol | Get the number of columns of an 'IntervalMatrix' object | 
| ncol-method | Get the number of columns of an 'IntervalMatrix' object | 
| nrow | Get the number of rows of an 'IntervalMatrix' object | 
| nrow-method | Get the number of rows of an 'IntervalMatrix' object | 
| plot | Plot a single interval or a list of intervals | 
| plot-method | Plot a single interval or a list of intervals | 
| rbind | Combine 'IntervalList' and 'IntervalMatrix' objects by rows | 
| rbind-method | Combine 'IntervalList' and 'IntervalMatrix' objects by rows | 
| show | Print basic information of interval-valued data | 
| show-method | Print basic information of interval-valued data | 
| simulIVS | Simulation of interval-valued responses to a questionnaire | 
| spr | Extract and replace the spreads of interval-valued objects | 
| spr-method | Extract and replace the spreads of interval-valued objects | 
| spr<- | Extract and replace the spreads of interval-valued objects | 
| spr<--method | Extract and replace the spreads of interval-valued objects | 
| sum | Calculate the sum of n intervals | 
| sum-method | Calculate the sum of n intervals | 
| var | Calculate the sample Fréchet variance of a random interval | 
| var-method | Calculate the sample Fréchet variance of a random interval | 
| [-method | Extract and replace parts of an interval-valued object | 
| [<--method | Extract and replace parts of an interval-valued object | 
| [[-method | Extract and replace parts of an interval-valued object | 
| [[<--method | Extract and replace parts of an interval-valued object |