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Testing Statistical Hypothesis Independent Sample t-Test

Testing Statistical Hypothesis Independent Sample t-Test. Heibatollah Baghi, and Mastee Badii. Example of Independent Groups t-tests.

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Testing Statistical Hypothesis Independent Sample t-Test

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  1. Testing Statistical HypothesisIndependent Sample t-Test Heibatollah Baghi, and Mastee Badii

  2. Example of Independent Groups t-tests • Suppose that we plan to conduct a study to alleviate the distress of preschool children who are about to undergo the finger-stick procedure for a hematocrit (Hct) determination. • Note: Hct = % of volume of a blood sample occupied by cells.

  3. Example of Independent Groups t-tests, Continued • Twenty subjects will be used to examine the effectiveness of the special treatment. • 10 subjects randomly assigned to treatment group. • 10 assigned to a control group that receives no special preparation.

  4. 1. Determine the Appropriate Test • Testing hypothesis about two independent means (t-test) • Dependent variable = the child’s pulse rate just prior to the finger-stick • Independent variable or grouping variable = treatment conditions (2 levels)

  5. 1. Determine the Appropriate Test • Two samples are independent. • Two populations are normally distributed. • The assumption of homogeneity of variance. (Examine Levene’s Test) Ho: 12 = 12 Ha: 12  12 If sig. level or p-value is > .05, the assumption is met.

  6. 2. Establish Level of Significance • The convention • α = .05 • α = .01 • α = .001 • In this example, assume α = 0.05

  7. 3. Determine Whether to Use a One or Two Tailed Test • H0 : µ1 = µ2 • Ha : µ1 µ2 • Where • µ1 = population mean for the experimental group • µ2 = population mean for the control group

  8. 4. Calculating Test Statistics

  9. Experimental Group Control Group Rearrange the Data

  10. 4. Calculating Test Statistics (continued) Group 1 (Experimental) Group 2 (Control) -------------------------------------------------------------------------------------------------- X1 X2 ------------ --------------

  11. 4. Calculating Test Statistics (continued)

  12. 6. Compare the Computed Test Statistic Against a Tabled Value

  13. 6. Compare the Computed Test Statistic Against a Tabled Value • If we had chosen a one tail test: • H0 : µ1 = µ2 • Ha : µ1 <µ2 1.73 The null hypothesis can be rejected

  14. SPSS Output for Two Sample Independent t-test Example

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