Table 1.

Personal estimates of caffeine consumption (milligrams) in young adults

	Consume irregularly <100 mg/wk		Consume regularly >100 mg/wk
	Per day	Per week	Per day	Per week
n	10	10	15	15
Mean	6	43	132	926
s.e.m.	2	12	34	239
t-test			P<0.05	P<0.05

n, sample size; mean, average milligrams consumed each day and each week; s.e.m., standard error of the mean; t-test, Students t-test for unequal sample sizes with unequal variances. Data above these P values are significantly different from corresponding data in columns labelled ‘consume irregularly’.