ci.m

calculates 90, 95 or 99% confidence interval.

interval=ci(x,confidence,dim);

90%, 95% or 99% confidence interval of a vector or 2d matrix
Optional dim refers to dimension and must be 1 or 2 (default is 1).
Optional confidence must either 90, 95 or 99 (default is 95).

Calculated as the standard error multiplied by the critical two-tailed value of t for a=0.10, 0.05 or 0.01 (see Statistical methods in psychology, D.C. Howell). This formula applies when the Population standard deviation is unknown. As n gets larger then the t distribution approaches the normal distribution. So, if n>120, uses z instead of t (e.g. 1.96 standard errors, for 95% interval)

Raymond Reynolds 23/11/06