Glossary
Definitions of 10 statistical, methodological, and governance terms that recur across our evaluations. Authored and signed off by the editorial team.
Statistics
Bland-Altman Plot
A Bland-Altman plot visualizes agreement between two measurement methods by plotting the difference between the methods against the average of the methods, with limits of agreement at ±1.96 standard deviations from the mean difference.
MAD
Mean Absolute Deviation (MAD) is the median of the absolute deviations from the median of the error set. It is a dispersion measure complementary to MAE and MAPE, capturing the concentration of the error distribution rather than its central tendency.
MAE
Mean Absolute Error (MAE) is the average per-meal absolute prediction error in kilocalories, before normalization by ground-truth value. It complements MAPE by preserving the absolute size of the error.
MAPE
Mean Absolute Percentage Error (MAPE) is the headline accuracy metric used in Methodology v3.2. It is the average of per-meal absolute percentage errors across the 50-meal weighed reference battery, expressed as a percentage.
Governance
Methodology
Evidence Grade
An evidence grade is a categorical assessment of the quality of evidence supporting a claim, typically based on study design, risk of bias, consistency, and replication. Methodology v3.2 uses a GRADE-aligned framework adapted for consumer software.
Ground Truth
Ground truth is the laboratory-established true value against which a measurement instrument's output is compared. For Methodology v3.2's accuracy battery, ground truth is the calorie content of weighed reference meals computed from USDA FoodData Central per-component values.
Replicability
Replicability is the property that an accuracy claim survives independent reproduction by a different research group using a comparable protocol. It is weighted at 15% of the composite under Methodology v3.2.
Validation Study
A validation study is a research protocol that evaluates whether a measurement instrument produces values that agree with a reference standard. For consumer calorie-tracking apps, validation studies measure MAPE against weighed reference meals.
Weighed Portion Reference
A weighed portion reference is a meal or food item whose true calorie and macronutrient content is established by gram-weighing each ingredient on a calibrated scale and computing values from USDA FoodData Central. It is the laboratory ground truth in Methodology v3.2.