T-test functions
T-test functions are used for statistical examination of two population means. A two-sample t-test examines whether two samples are different and is commonly used when two normal distributions have unknown variances and when an experiment uses a small sample size.

In the following sections, the t-test statistical test functions are grouped according to the sample student test that applies to each type of function.

Use the drop-down on each function to see a brief description and the syntax of each function. Click the function name in the syntax description for further details.

See: Creating a typical t-test report

Two independent samples t-tests
The following functions apply to two independent samples student's t-tests:

ttest_conf
TTest_conf returns the aggregated t-test confidence interval value for two independent samples.

ttest_conf (
grp, value [, sig[, eq_var]])

ttest_df
TTest_df() returns the aggregated student's t-test value (degrees of freedom)
for two independent series of values.

ttest_df ( grp, value [, eq_var)

ttest_dif
TTest_dif() is a numeric function that returns the aggregated student's t-test mean difference for two independent series of values.

ttest_dif ( grp, value)

ttest_lower
TTest_lower() returns the aggregated value for the lower end of the confidence interval
for two independent series of values.

ttest_lower ( grp, value [, sig[, eq_var]])

ttest_sig
TTest_sig() returns the aggregated student's t-test 2-tailed level of significance for two independent series of values.

ttest_sig ( grp, value [, eq_var])

ttest_sterr
TTest_sterr() returns the aggregated student's t-test standard error of the mean difference for two independent series of values.

ttest_sterr ( grp, value [, eq_var])

ttest_t
TTest_t() returns the aggregated t value for two independent series of values.

ttest_t ( grp, value
[, eq_var])

ttest_upper
TTest_upper() returns the aggregated value for the upper end of the confidence interval
for two independent series of values.

ttest_upper ( grp, value [, sig [, eq_var]])

Two independent weighted samples t-tests
The following functions to two independent samples student's t-tests where the input data series is given in weighted two-column format:

ttestw_conf
TTestw_conf() returns the aggregated t value for two independent series of values.

ttestw_conf ( weight, grp, value [, sig[, eq_var]])

ttestw_df
TTestw_df() returns the aggregated student's t-test df value (degrees of freedom) for two independent series of values.

ttestw_df ( weight, grp,
value [, eq_var])

ttestw_dif
TTestw_dif() returns the aggregated student's t-test mean difference for two independent
series of values.

ttestw_dif (
weight, grp, value)

ttestw_lower
TTestw_lower() returns the aggregated value for the lower end of the confidence interval for two independent series of values.

ttestw_lower ( weight, grp,
value [, sig[, eq_var]])

ttestw_sig
TTestw_sig() returns the aggregated student's t-test 2-tailed level of significance
for two independent series of values.

ttestw_sig (
weight, grp, value [, eq_var])

ttestw_sterr
TTestw_sterr() returns the aggregated student's t-test standard error of the mean difference
for two independent series of values.

ttestw_sterr ( weight, grp,
value [, eq_var])

ttestw_t
TTestw_t() returns the aggregated t value for two independent series of values.

ttestw_t ( weight, grp,
value [, eq_var])

ttestw_upper
TTestw_upper() returns the aggregated value for the upper end of the confidence interval
for two independent series of values.

ttestw_upper ( weight, grp,
value [, sig [, eq_var]])

One sample t-tests
The following functions apply to one-sample student's t-tests:

ttest1_conf
TTest1_conf() returns the aggregated confidence interval value for a series of values.

ttest1_conf ( value [,
sig])

ttest1_df
TTest1_df() returns the aggregated student's t-test df value (degrees of freedom)
for a series of values.

ttest1_df ( value)

ttest1_dif
TTest1_dif() returns the aggregated student's t-test mean difference for a series of values.

ttest1_dif ( value)

ttest1_lower
TTest1_lower() returns the aggregated value for the lower end of the confidence interval for a series of values.

ttest1_lower ( value [,
sig])

ttest1_sig
TTest1_sig() returns the aggregated student's t-test 2-tailed level of significance
for a series of values.

ttest1_sig ( value)

ttest1_sterr
TTest1_sterr() returns the aggregated student's t-test standard error of the mean difference for a series of values.

ttest1_sterr ( value)

ttest1_t
TTest1_t() returns the aggregated t value for a series of values.

ttest1_t ( value)

ttest1_upper
TTest1_upper() returns the aggregated value for the upper end of the confidence interval for a series of values.

ttest1_upper ( value [,
sig])

One weighted sample t-tests
The following functions apply to one-sample student's t-tests where the input data series is given in weighted two-column format:

ttest1w_conf
TTest1w_conf() is a numeric function that returns the aggregated confidence interval value for a series of values.

ttest1w_conf ( weight, value [, sig])

ttest1w_df
TTest1w_df() returns the aggregated student's t-test df value (degrees of freedom)
for a series of values.

ttest1w_df ( weight, value)

ttest1w_dif
TTest1w_dif() returns the aggregated student's t-test mean difference for a series of values.

ttest1w_dif ( weight, value)

ttest1w_lower
TTest1w_lower() returns the aggregated value for the lower end of the confidence interval for a series of values.

ttest1w_lower ( weight, value [, sig])

ttest1w_sig
TTest1w_sig() returns the aggregated student's t-test 2-tailed level of significance
for a series of values.

ttest1w_sig ( weight, value)

ttest1w_sterr
TTest1w_sterr() returns the aggregated student's t-test standard error of the mean difference for a series of values.

ttest1w_sterr ( weight, value)

ttest1w_t
TTest1w_t() returns the aggregated t value for a series of values.

ttest1w_t (
weight, value)

ttest1w_upper
TTest1w_upper() returns the aggregated value for the upper end of the confidence interval
for a series of values.

ttest1w_upper ( weight, value [, sig])