statistical tests - T-test (test 1)

t test

statistical test evaluating the means of 2 groups

independent sample t test

• when these two groups are independent (or unrelated to one another), we can use a procedure known as the unpaired (AKA, independent-groups or two-sample) t test.

• unmodified use of “t test” implies this test.

• this independent t test tests for differences in two group means or compares means for two independent groups of cases.

normality

variable where the 2 groups are being compared is normally distributed in each population

variance

variances of the variable in the 2 populations are equal (called homogeneity f variance)

independence

observations within each group and between each group are independent, meaning that knowing the value of any one observation tells us nothing about the value of another observation

paired t test

• when we are comparing 2 means, this procedure is called the dependent groups

• the basic procedure for hypothesis testing and confidence interval estimation, as well as their interpretations, are essentially the same

1 sample t test

• used to determine whether an unknown population mean is different from a specific value.

• use the test for continuous data.

  • your data should be a random sample from a normal population.

• we need one variable

  • we also have an idea, or hypothesis, that the mean of the population has some value.