The t statistic: an alternative to z: when hypothesis testing: Use a sample mean m to approximate the. Standard error, m, measures how well m pop mean . approximates . Then compare m to by computing the relevant z-score test statistic. Use to determine whether the obtained dif is greater than expected by chance by looking at unit normal table (for a normal distribution: particular advantage of t statistic: Like z-score, t statistic allows researchers to use sample data to test hypotheses about an unknown . Doesn"t require any knowledge of the pop. So can be used to test hypotheses about a. Which we typically don"t know completely unknown pop, ie: Only available info about pop comes from sample: all required for a hypothesis test with t is a sample & a reasonable hypothesis about , when we don"t have can estimate it using the sample variability.