Economics, Nutrition and Family Budgets

Vol. 14 The National Food Survey of Great Britain households. From the nutritional aspect these families are of high importance, because they contained about a quarter of the children in all households surveyed. The annual average calcium intakes for these families can be obtained with a standard error of 0.8% so that differences between two sample annual averages must be just over 2% to achieve statistical significance at the 5% level. It follows therefore that the present sample sizes may be considered just adequate to detect long-term trends in the diet of this important section of the population. Fortunately any more or less constant bias (e.g. errors in nutrient conversion factors) has little effect on comparisons over time.