Case Studies

collage Many children and adults hold misconceptions about decimal notation. This section presents six case studies of people holding different misconceptions. Each case study contains:

results of the Decimal Comparison Test.
interviews of the person completing four tasks.
a short test to check your understanding of this thinking.
lesson ideas appropriate for a student with this misconception.

Case Study 1: Caitlin Whole Number Thinking These learners consider that the digits after the decimal point make another whole number.	Case Study 4: Brad Column Overflow Thinking These learners know column names but try to put more than one digit into a column.
Case Study 2: Courtney Reciprocal Thinking These learners interpret decimals as fractions.	Case study 5: Tuyet Reverse Thinking These learners have not heard the 'th' sound in the column names.
Case Study 3: Ricardo Denominator Focussed Thinking These learners know that tenths are larger than hundredths, but think that any number of tenths is larger than any number of hundredths.	Case Study 6: Maria Money Thinking These learners make an analogy with dollars and cents.

The case studies are derived from interviews with Australian children in Years 4 to 10 and with adults. They were conducted as part of the research study "Improving learning outcomes in numeracy" (funded by the Australian Research Council with chief investigators Professors Kaye Stacey and Liz Sonenberg) and Vicki Steinle's PhD thesis. The identities of interviewees have been changed. Interviews have been edited, amalgamated and some parts have been 'created', to present the reasoning clearly.