Part II: Introduction to Hypothesis Testing
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Part II: Introduction to Hypothesis Testing. Chapter 9 Two-Sample Tests. Renee R. Ha, Ph.D. James C. Ha, Ph.D. Integrative Statistics for the Social & Behavioral Sciences. Paired t test. Also called Correlated Groups t test. Paired t test. Use when:

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Chapter 9 Two-Sample Tests

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Chapter 9 two sample tests

Part II: Introduction to Hypothesis Testing

Chapter 9

Two-Sample Tests

Renee R. Ha, Ph.D.

James C. Ha, Ph.D

Integrative Statistics for the Social & Behavioral Sciences


Paired t test

Paired t test

  • Also called Correlated Groups t test


Paired t test1

Paired t test

  • Use when:

    • You have two measures on the same subjects (“before” and “after” measures are common).

    • You have two separate samples but the subjects in each are individually matched so that there are similar subjects in each group (but not the same subjects in each group).


Tables 9 1 9 2

Tables 9.1 & 9.2

  • Table 9.1: An example of “before” and “after” pairing using the same subjects in each “paired” sample

  • Table 9.2: An example of a “paired” design in which the actual subjects in each sample are different but are “matched” for characteristics which they have in common (in this example, genetics)


Formulas

Formulas


Working formula paired t test

Working Formula: Paired t test


T test paired two sample for means

t-Test: Paired Two Sample for Means

  • Results if you use Microsoft Excel to calculate the t-test


Paired samples test

Paired Samples Test

  • Results if you use SPSS to calculate the t-test


Chapter 9 two sample tests

t-Test: Paired Two Sample for Means

  • Results if you use Microsoft Excel to calculate the t-test


Chapter 9 two sample tests

Paired Samples Test

  • Results if you use SPSS to calculate the t-test


When to use paired t test

When to use Paired t test

1. You have two samples and a within-groups design.

2. The sampling distribution is normally distributed.

3. The dependent variable is on an interval or ratio scale.


Independent t test

Independent t test

  • Two completely different (independent) groups of subjects that you want to compare to determine if they are significantly different from one another: a between-groups design.

  • E.g. Experimental and control conditions.

  • Compare the means of the two conditions/groups.


Independent t test1

Independent t test

  • Sampling Distribution of the Difference between sample means.

  • Determining variance when you have TWO estimates.


Weighted variance

Weighted Variance


Formula independent t test

Formula Independent t test


Independent t test formulas

Independent t test Formulas


T test two sample assuming equal variances

t-Test: Two-Sample Assuming Equal Variances

  • Results if you use Microsoft Excel to calculate the t-test


Independent samples test

Independent Samples Test

  • Results if you use SPSS to calculate the t-test


Chapter 9 two sample tests

t-Test: Two-Sample Assuming Equal Variances

  • Results if you use Microsoft Excel to calculate the t-test


Chapter 9 two sample tests

Independent Samples Test

  • Results if you use SPSS to calculate the t-test


When to use independent t test

When to use Independent t test

1. Two samples and a between-groups design.

2. The sampling distribution is normally distributed.

3. The dependent variable is on an interval or ratio scale

4. The variances of the two groups are the same or are homogeneous.


Chapter 9 two sample tests

HOV

The homogeneity of variance assumption (HOV) requires that the variances of the underlying populations are equal or, in practical terms, not significantly different from one another.


Effect sizes and power

Effect Sizes and Power


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