A paired t-test is used when we are interested in the difference between two variables for the same subject. Often the two variables are separated by time. ... Since we are ultimately concerned with the difference between two measures in one sample, the paired t-test reduces to the one sample t-test.

What is the difference between t-test and paired t-test?

Two-sample t-test is used when the data of two samples are statistically independent, while the paired t-test is used when data is in the form of matched pairs.

What does the paired t-test tell you?

The paired t-test, also referred to as the paired-samples t-test or dependent t-test, is used to determine whether the mean of a dependent variable (e.g., weight, anxiety level, salary, reaction time, etc.) is the same in two related groups (e.g., two groups of participants that are measured at two different "time ...

When should a paired t-test be performed instead of a two-sample t test?

A paired t-test should be performed instead of a two-sample t-test when each observation in one group categorical sample are dependent.

What are the assumptions for a paired t test?

Paired t-test assumptions

Subjects must be independent. Measurements for one subject do not affect measurements for any other subject. Each of the paired measurements must be obtained from the same subject. For example, the before-and-after weight for a smoker in the example above must be from the same person.

Paired t Test | Statistics Tutorial #21| MarinStatsLectures

24 related questions found

Why would you use a two sample t test?

The two-sample t-test (Snedecor and Cochran, 1989) is used to determine if two population means are equal. A common application is to test if a new process or treatment is superior to a current process or treatment. There are several variations on this test.

What is difference between paired and unpaired t-test?

A paired t-test is designed to compare the means of the same group or item under two separate scenarios. An unpaired t-test compares the means of two independent or unrelated groups. In an unpaired t-test, the variance between groups is assumed to be equal.

When should a paired t-test be conducted?

A paired t-test is used when we are interested in the difference between two variables for the same subject. Often the two variables are separated by time. For example, in the Dixon and Massey data set we have cholesterol levels in 1952 and cholesterol levels in 1962 for each subject.

What is the purpose of t-test in research?

A t-test is a type of inferential statistic used to determine if there is a significant difference between the means of two groups, which may be related in certain features. The t-test is one of many tests used for the purpose of hypothesis testing in statistics.

What is the main difference between paired and independent samples?

Paired-samples t tests compare scores on two different variables but for the same group of cases; independent-samples t tests compare scores on the same variable but for two different groups of cases.

What is the t-value in a paired t test?

This t-value indicates that the difference is 3 times the size of the standard error.

What does a negative t-value mean in a paired t test?

Find a t-value by dividing the difference between group means by the standard error of difference between the groups. A negative t-value indicates a reversal in the directionality of the effect, which has no bearing on the significance of the difference between groups.

When would you use a paired difference t test quizlet?

When do you use a paired t test? When there is a within subjects design, and each of the subjects has completed a variation of the same test twice. You just studied 31 terms!

What is the difference between paired and unpaired data?

Paired means that both samples consist of the same test subjects. A paired t-test is equivalent to a one-sample t-test. Unpaired means that both samples consist of distinct test subjects.

Is a Student's t-test paired or unpaired?

Paired t-test compares study subjects at 2 different times (paired observations of the same subject). Unpaired t-test (aka Student's test) compares two different subjects.

Is a paired t-test two tailed?

Like many statistical procedures, the paired sample t-test has two competing hypotheses, the null hypothesis and the alternative hypothesis. ... The alternative hypothesis can take one of several forms depending on the expected outcome. If the direction of the difference does not matter, a two-tailed hypothesis is used.

How do I know if my data is paired?

Two data sets are "paired" when the following one-to-one relationship exists between values in the two data sets.

1. Each data set has the same number of data points.
2. Each data point in one data set is related to one, and only one, data point in the other data set.

What is the difference between a one sample t test and a two sample t test?

If you are studying one group, use a paired t-test to compare the group mean over time or after an intervention, or use a one-sample t-test to compare the group mean to a standard value. If you are studying two groups, use a two-sample t-test. If you want to know only whether a difference exists, use a two-tailed test.

Why do we tend to use two-tailed tests in psychology?

We use a two-tailed test because we care whether the mean is greater than or less than the target value. To interpret the results, simply compare the p-value to your significance level.

What are the conditions for a 2 sample t-test?

Two-sample t-test assumptions

• Data values must be independent. ...
• Data in each group must be obtained via a random sample from the population.
• Data in each group are normally distributed.
• Data values are continuous.
• The variances for the two independent groups are equal.

Which t-test should I use?

If you are studying one group, use a paired t-test to compare the group mean over time or after an intervention, or use a one-sample t-test to compare the group mean to a standard value. If you are studying two groups, use a two-sample t-test. If you want to know only whether a difference exists, use a two-tailed test.

What does T value tell you?

The t-value measures the size of the difference relative to the variation in your sample data. Put another way, T is simply the calculated difference represented in units of standard error. The greater the magnitude of T, the greater the evidence against the null hypothesis.

What are the degrees of freedom for a paired t-test?

Normally, there are n − 1 degrees of freedom (with n being the total number of observations). A paired samples t-test based on a "matched-pairs sample" results from an unpaired sample that is subsequently used to form a paired sample, by using additional variables that were measured along with the variable of interest.