This article presents the results of an internal reliability analysis of a questionnaire designed to evaluate the presence of mathematical processes in the practices used to teach and learn mathematics. After validating the instrument by means of expert judgement in a prior study, 20 expert evaluators administered the instrument to 95 teachers of preschool and primary education in the Community of Murcia (Spain). The data obtained was analysed with the R-3.1.0 statistical package on an i686-pc-linux-gnu (32-bit) platform. Based on standardised scores, the Cronbach alpha shows a good level of internal consistency (median alpha coefficient .789 for Preschool and .86 for Primary), with the lowest level corresponding to the process of "representation" in preschool, with value of .74, which is still considered to be an acceptable level of internal consistency.