Two groups of individuals were compared with respect to a high carbohydrate low-fat diet (LF) and a high-fat low carbohydrate diet (LC). Mood was assessed using a total mood disturbance score where a lower score is associated with a less negative mood. Assuming that the random samples come from independent normal distributions with a common but unknown variance, construct a 95% confidence interval for the difference between the two population means, LC less LF.

Group	n	mean	standard deviation
LC	12	47.3	28.3
LF	13	19.3	25.8