Thinking about and working with different variables presents students with a variety of difficulties (Table 1, difficulty II, A F).
While we classified these as established difficulties, we found only one study that exposed difficulties science nonmajors' have graphically representing categorical variable data (Table 1, difficulty IIA).
Student difficulties with natural variability have been well documented in multiple studies examining students doing experiments (Table 1, difficulty IV).
The characteristics of rating scales that demonstrated functional response options are shown in Table 3 (difficulty and frequency) and Table 4 (severity and global vision).
Students from elementary school (Chen and Klahr, 1999), middle school (Tobin and Capie, 1982), and undergraduate levels (Tobin and Capie, 1981; Lawson et al., 2000) struggle with estimating the extent of inferences made from experimental findings (Table 1, difficulty V).
Table 4 Difficulties expressed by local residents regarding relocation in the Akuressa area of Sri Lanka Difficulties regarding relocation Number of respondents Nowhere to go 6 Financial 5 No equivalent place to live 4 Oldest man of the house doesn't want to move 1 Don't know how to look for a new place 1. Age group, gender, and location comparisons revealed interesting differences.
As examples for scoring a particular assessment, a table with difficulties from the shrimp assessment and drug assessment are posted online (http://tinyurl.com/REDShrimp and http://tinyurl.com/REDDrug).
As shown in Table 1, difficulties were found across different populations of students at multiple educational levels, including elementary, middle, and high school students, undergraduates who were not science majors, and undergraduate science students.
These goals align with some of the Table 1 difficulties, because groups of experimental subjects to be tested should be considered based on a variable property appropriate for the goal of an investigation (difficulty I), and a treatment was to be applied to groups of birds as experimental subjects (difficulty II, C and F).
Table 3 Item difficulty by major compared to average difficulty for all groups* Person class Count DIF score DIF measure DIF Size DIF S.E.
