T-tests: comparing two vectors

Functions

double apop_db_t_test (char *tab1, char *col1, char *tab2, char *col2)
double apop_db_paired_t_test (char *tab1, char *col1, char *col2)
apop_data * apop_t_test (gsl_vector *a, gsl_vector *b)
apop_data * apop_paired_t_test (gsl_vector *a, gsl_vector *b)

Detailed Description

Function Documentation

double apop_db_paired_t_test	(	char *	tab1,
		char *	col1,
		char *	col2
	)

Do a paired t-test entirely inside the database. Returns only the two-tailed p-value.

double apop_db_t_test	(	char *	tab1,
		char *	col1,
		char *	tab2,
		char *	col2
	)

Do a t-test entirely inside the database. Returns only the two-tailed p-value.

apop_data* apop_paired_t_test	(	gsl_vector *	a,
		gsl_vector *	b
	)

Answers the question: with what confidence can I say that the mean difference between the two columns is zero?

Parameters:

{a,b}

two columns of data

Returns:: an apop_data set with the following elements: mean left - right: the difference in means; if positive, first vector has larger mean, and one-tailed test is testing , else reverse if negative.
t statistic: used for the test
df: degrees of freedom
p value, 1 tail: the p-value for a one-tailed test that one vector mean is greater than the other. confidence, 1 tail: 1- p value. p value, 2 tail: the p-value for the two-tailed test that left mean = right mean. confidence, 2 tail: 1-p value

apop_data* apop_t_test	(	gsl_vector *	a,
		gsl_vector *	b
	)

Answers the question: with what confidence can I say that the means of these two columns of data are different? apop_paired_t_test answers the question: with what confidence can I say that the mean difference between the two columns is zero?

If apop_opts.verbose is nonzero, then display some information, like the mean/var/count for both vectors and the t statistic, to STDOUT.