The dependent t-test (also called the paired t-test or paired-samples t-test) compares the means of two related groups to determine whether there is a statistically significant difference between these means. What variables do you need for a dependent t-test?
Full Answer
Can a t-test be used to compare two groups?
A t-test should not be used to measure differences among more than two groups, because the error structure for a t-test will underestimate the actual error when many groups are being compared. If you want to compare the means of several groups at once, it’s best to use another statistical test such as ANOVA or a post-hoc test.
What is a t test used for in research?
A t-test is a statistical test that is used to compare the means of two groups. It is often used in hypothesis testing to determine whether a process or treatment actually has an effect on the population of interest, or whether two groups are different from one another.
What is the difference between independent t test and paired t test?
1 An independent sample t-test is used when we want to compare the mean of two groups. 2 A paired sample t-test is used when we want to compare the mean of the same group but at different points of time. 3 One sample t-test is used when we are in need of checking the mean of an individual group against an unknown mean.
Why do we use a two-tailed t-test?
You don’t care about the direction of the difference, only whether there is a difference, so you choose to use a two-tailed t-test. The t-test estimates the true difference between two group means using the ratio of the difference in group means over the pooled standard error of both groups.
What type of t-test should be used to compare the two methods and why?
When to use a t-test. A t-test can only be used when comparing the means of two groups (a.k.a. pairwise comparison). If you want to compare more than two groups, or if you want to do multiple pairwise comparisons, use an ANOVA test or a post-hoc test.
How do you know if there is a significant difference between two groups t-test?
To do this: determine the degrees of freedom, and look up the critical value in the table in the back of the book for alpha=. 05 (in Daniel's tables, the subscript value . 975 is used). If the value you calculated exceeds the value in the table, it is significant (i.e., the null hypothesis is rejected).
What type of 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 statistical treatment should you use if you want to test the significant difference between two variables?
A one-way analysis of variance (ANOVA) is used when you have a categorical independent variable (with two or more categories) and a normally distributed interval dependent variable and you wish to test for differences in the means of the dependent variable broken down by the levels of the independent variable.
When do we use t-test and Z-test?
As mentioned, a t-test is primarily used for research with limited sample sizes whereas a z-test is deployed for hypothesis testing that requires researchers to look at a population size that's larger than 30.
What is at test and Z-test?
Content: T-test Vs Z-test T-test refers to a type of parametric test that is applied to identify, how the means of two sets of data differ from one another when variance is not given. Z-test implies a hypothesis test which ascertains if the means of two datasets are different from each other when variance is given.
What is a Type 3 t-test?
3–This implies that a two-sample unequal variance t-test (or the Welch t-test) is to be performed. One must perform this test when there are two independent samples having unequal or unknown variances. The feature of unequal variances is known as heteroscedasticity.
What is chi-square test used for?
A chi-square test is a statistical test used to compare observed results with expected results. The purpose of this test is to determine if a difference between observed data and expected data is due to chance, or if it is due to a relationship between the variables you are studying.
What is a two-tailed t-test?
A two-tailed test, in statistics, is a method in which the critical area of a distribution is two-sided and tests whether a sample is greater than or less than a certain range of values. It is used in null-hypothesis testing and testing for statistical significance.
What statistical test should I use to compare two groups?
When comparing more than two sets of numerical data, a multiple group comparison test such as one-way analysis of variance (ANOVA) or Kruskal-Wallis test should be used first.
What is the best statistical test to compare two groups?
The two most widely used statistical techniques for comparing two groups, where the measurements of the groups are normally distributed, are the Independent Group t-test and the Paired t-test.
Which of the following statistical test is used to compare 2 or more group?
Choosing a statistical testType of DataCompare two unpaired groupsUnpaired t testMann-Whitney testCompare two paired groupsPaired t testWilcoxon testCompare three or more unmatched groupsOne-way ANOVAKruskal-Wallis testCompare three or more matched groupsRepeated-measures ANOVAFriedman test6 more rows•Mar 23, 2012
What is a t-test?
A t-test is a statistical test that compares the means of two samples . It is used in hypothesis testing , with a null hypothesis that the di...
What does a t-test measure?
A t-test measures the difference in group means divided by the pooled standard error of the two group means. In this way, it calculates a numbe...
Which t-test should I use?
Your choice of t-test depends on whether you are studying one group or two groups, and whether you care about the direction of the difference in...
What is the difference between a one-sample t-test and a paired t-test?
A one-sample t-test is used to compare a single population to a standard value (for example, to determine whether the average lifespan of a speci...
Can I use a t-test to measure the difference among several groups?
A t-test should not be used to measure differences among more than two groups, because the error structure for a t-test will underestimate the ac...
Confidence Interval For The Mean from A Small Sample
A rare congenital disease, Everley's syndrome, generally causes a reduction in concentration of blood sodium. This is thought to provide a useful d...
Difference Between Means of Two Samples
Here we apply a modified procedure for finding the standard error of the difference between two means and testing the size of the difference by thi...
Unequal Standard Deviations
If the standard deviations in the two groups are markedly different, for example if the ratio of the larger to the smaller is greater than two, the...
Difference Between Means of Paired Samples (Paired T Test).
When the effects of two alternative treatments or experiments are compared, for example in cross over trials, randomised trials in which randomisat...
When to use a t-test?
When the difference between two population averages is being investigated, a t test is used. In other words, a t test is used when we wish to compare two means (the scores must be measured on an interval or ratio measurement scale ). We would use a t test if we wished to compare the reading achievement of boys and girls. With a t test, we have one independent variable and one dependent variable. The independent variable (gender in this case) can only have two levels (male and female). The dependent variable would be reading achievement. If the independent had more than two levels, then we would use a one-way analysis of variance (ANOVA).
Who first published a t-test?
William Sealy Gosset .pdf (1905) first published a t-test. He worked at the Guiness Brewery in Dublin and published under the name Student. The test was called Student Test (later shortened to t test). t tests can be easily computed with the Excel or SPSS computer application.
What is type 1 error?
Type I error —#N#reject a null hypothesis that is really true (with tests of difference this means that you say there was a difference between the groups when there really was not a difference). The probability of making a Type I error is the alpha level you choose. If you set your probability (alpha level) at p < 05, then there is a 5% chance that you will make a Type I error. You can reduce the chance of making a Type I error by setting a smaller alpha level (p < .01). The problem with this is that as you lower the chance of making a Type I error, you increase the chance of making a Type II error.
What is a T test?
A T-Test is a method used to derive an inference in statistics, which is aimed to find out if there is any major difference between two means wherein the two groups considered may be related to each other.
What is the second assumption of a t-test?
The second assumption can be regarding the random nature of the sample. This means that the data collected should be pure random in nature. The third assumption can be that when we plot the data related to t-test distribution, it should follow a normal distribution.
What is the purpose of the T test?
The T-Test is aimed at hypothesis testing, which basically is used to test a hypothesis pertaining to a given population. It tells us the level of significance of the difference between the groups, which are generally measured on the basis of the mean. Here we basically find out the difference between population means.
What is a class 5 aimed test?
It is aimed for testing if the mean of the value one has targeted is equal to the mean of a single population, e.g., Testing whether the average weight of Class 5 students are more than 45kg
When the effects of two alternative treatments or experiments are compared, for example in cross over trials, is it possible to
Matching controls for the matched variables, so can lead to a more powerful study.
What is the confidence interval for the mean from a small sample?
Confidence interval for the mean from a small sample. A rare congenital disease, Everley’s syndrome, generally causes a reduction in concentration of blood sodium. This is thought to provide a useful diagnostic sign as well as a clue to the efficacy of treatment.
How to find standard deviation in a sample?
Obtain the standard deviation in sample 1: Obtain the standard deviation in sample 2: Multiply the square of the standard deviation of sample 1 by the degrees of freedom, which is the number of subjects minus one: Repeat for sample 2. Add the two together and divide by the total degrees of freedom.
What is a t-test?
A t-test is used as a hypothesis testing tool, which allows testing of an assumption applicable to a population . A t-test looks at the t-statistic, the t-distribution values, and the degrees of freedom to determine the statistical significance. To conduct a test with three or more means, one must use an analysis of variance .
When is a correlated t-test performed?
The correlated t-test is performed when the samples typically consist of matched pairs of similar units, or when there are cases of repeated measures. For example, there may be instances of the same patients being tested repeatedly—before and after receiving a particular treatment. In such cases, each patient is being used as a control sample against themselves.
What is the standard procedure of trying a drug on one group of patients and giving a placebo to another group?
It follows the standard procedure of trying the drug on one group of patients and giving a placebo to another group, called the control group . The placebo given to the control group is a substance of no intended therapeutic value and serves as a benchmark to measure how the other group, which is given the actual drug, responds.
How many data values are needed for a t-test?
Calculating a t-test requires three key data values. They include the difference between the mean values from each data set (called the mean difference), the standard deviation of each group, and the number of data values of each group.
What are the two outputs of a t-test?
The t-test produces two values as its output: t-value and degrees of freedom. The t-value is a ratio of the difference between the mean of the two sample sets and the variation that exists within the sample sets. While the numerator value (the difference between the mean of the two sample sets) is straightforward to calculate, the denominator (the variation that exists within the sample sets) can become a bit complicated depending upon the type of data values involved. The denominator of the ratio is a measurement of the dispersion or variability. Higher values of the t-value, also called t-score, indicate that a large difference exists between the two sample sets. The smaller the t-value, the more similarity exists between the two sample sets.
What does a large t score mean?
A large t-score indicates that the groups are different. A small t-score indicates that the groups are similar. Degrees of freedom refers to the values in a study that has the freedom to vary and are essential for assessing the importance and the validity of the null hypothesis.
When to use equal variance t-test?
The equal variance t-test is used when the number of samples in each group is the same, or the variance of the two data sets is similar. The following formula is used for calculating t-value and degrees of freedom for equal variance t-test:
What is a one sample t-test?
The one-sample t-test, also known as the single-parameter t test or single-sample t-test, is used to compare the mean of one sample to a known standard (or theoretical / hypothetical) mean.
What is paired t-test?
The paired t-test is used to compare the means of two related groups of samples. Put into another words, it’s used in a situation where you have two values (i.e., pair of values) for the same samples.
Which test is less restrictive?
the Welch’s t-test, which is less restrictive compared to the original Student’s test. This is the test where you do not assume that the variance is the same in the two groups, which results in the fractional degrees of freedom.
What does it mean when the interval contains 0?
The fact that the interval contains 0 means that if you had performed a test of the hypothesis that the two population means are different (using the same significance level), you would not have been able to reject the null hypothesis of no difference.
Is intensive tutoring more effective than paced tutoring?
An experiment is conducted to determine whether intensive tutoring (covering a great deal of material in a fixed amount of time) is more effective than paced tutoring (covering less material in the same amount of time). Two randomly chosen groups are tutored separately and then administered proficiency tests.
