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.
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How is paired sample t-test used?
Running the Test
- Click Analyze > Compare Means > Paired-Samples T Test.
- Select the variable English and move it to the Variable1 slot in the Paired Variables box. Then select the variable Math and move it to the Variable2 slot in the Paired Variables box.
- Click OK.
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 paired t-test mean in statistics?
A paired t-test is used to compare two population means where you have two samples in which observations in one sample can be paired with observations in the other sample.
When can an unpaired t-test be used?
When to use an unpaired t-test? An unpaired t-test is used to compare the mean between two independent groups. You use an unpaired t-test when you are comparing two separate groups with equal variance.
How do you interpret a paired samples t-test?
Complete the following steps to interpret a paired t-test.
- Step 1: Determine a confidence interval for the population mean difference. First, consider the mean difference, and then examine the confidence interval.
- Step 2: Determine whether the difference is statistically significant.
- Step 3: Check your data for problems.
What does it mean when data is paired?
Paired data is where natural matching or coupling is possible. Generally this would be data sets where every data point in one independent sample would be paired—uniquely—to a data point in another independent sample.
When should 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 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 an advantage of using a matched pair or dependent samples design over an independent samples design?
Now the two groups are matched in terms of both age and gender. Differences between the group means can no longer be explained by differences in age or gender of the participants. The primary advantage of the matched pairs design is to use experimental control to reduce one or more sources of error variability.
What is p value in paired t-test?
The P-value is the probability of finding the observed difference (or larger) between the paired samples, under the null-hypothesis. The null-hypothesis is the hypotheses that in the population (from which the samples are drawn) the difference between similarly paired observations is 0.
What is the difference between paired and unpaired samples?
There are two types: paired and unpaired. 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.
What is a disadvantage of a paired samples t-test?
However, a paired t-test comes with the following potential cons: The potential for sample size reduction. If an individual drops out of the study, the sample size of each group is reduced by one since that individual appears in each group. The potential for order effects.
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.
Why is paired data useful?
The idea of paired data is contrasted with the usual association of one number to each data point as in other quantitative data sets in that each individual data point is associated with two numbers, providing a graph that allows statisticians to observe the relationship between these variables in a population.
What are paired observations?
Paired data arise when two of the same measurements are taken from the same subject, but under different experimental conditions. Subjects often receive both a treatment Y1 and a control Y2. Pairing observations reduces the subject-to-subject variability in the response.
How do you know if data should be paired?
Two data sets are “paired” when the following one-to-one relationship exists between values in the two data sets.
- Each data set has the same number of data points.
- Each data point in one data set is related to one, and only one, data point in the other data set.
What are some of the main uses for hypothesis testing on two samples?
In statistical hypothesis testing, a two-sample test is a test performed on the data of two random samples, each independently obtained from a different given population. The purpose of the test is to determine whether the difference between these two populations is statistically significant.
Why do we use t-test in research?
Essentially, a t-test allows us to compare the average values of the two data sets and determine if they came from the same population.Statisticians must additionally use tests other than the t-test to examine more variables and tests with larger sample sizes. For a large sample size, statisticians use a z-test.
Should you use two-sample t procedure on paired data?
Because the two samples are independent, you must use the 2-sample t test to compare the difference in the means. If you use the paired t test for these data, Minitab assumes that the before and after scores are paired: The 47 score before training is associated with a 53 score after training.
What is a paired study?
Paired samples (also called dependent samples) are samples in which natural or matched couplings occur. This generates a data set in which each data point in one sample is uniquely paired to a data point in the second sample.The “opposite” of paired samples is independent samples.