Week 8 - Assignment: Signature Assignment: Create a Presentation for Statistical Analysis in Research

SAGE Research Methods Video

t Test

Video Title: t Test

Originally Published: 2016

Publication Date: Sep. 30, 2016

Publishing Company: SAGE Publications, Inc.

City: Thousand Oaks, United States

ISBN: 9781506359137

DOI: https://dx.doi.org/10.4135/9781506359137

(c) SAGE Publications Inc., 2017

HERSCHEL KNAPP: Welcome to Practical Statistics for Nursing Using SPSS. [PRACTICAL STATISTICS FOR NURSING USING SPSS-- HERSCHEL KNAPP] This video shows how to process the t Test. [t Test] You can watch the entire video or use the time slider to navigate directly to any time point. [t Test-- Overview] The t Test compares two groups of continuous variables

HERSCHEL KNAPP [continued]: to determine if one group statistically significantly outperformed the other. In this example, we have two groups. The members of each group will be given an anti- hypertensive drug. The participants in Group 1 get Drug A, and the participants in Group 2 get Drug B. After a month, we'll record the systolic blood

HERSCHEL KNAPP [continued]: pressure of each participant. Group 1 had a mean of 120.37, and Group 2 had a mean of 122.37. The t Test will compare the groups to each other and compute the p value. If the p value is less than or equal to 0.05, we would conclude that one drug statistically significantly

HERSCHEL KNAPP [continued]: outperformed the other. [Since p is less than or equal to 0.05, we conclude that Drug A (mu = 120.37) stastitically outperformed Drug B (mu = 122.37)] This example uses the dataset Ch 05 Example 01 t Test.sav. [t Test-- Ch 05 - Example 01 - t Test.sav] This dataset contains two variables. The first variable is Group, which is a categorical variable containing two values.

HERSCHEL KNAPP [continued]: Group 1 gets Drug A and Group 2 gets Drug B. The second variable is systolicBP. This is a continuous variable that contains the systolic blood pressure reading of each participant. The t Test will compute the mean for each group and then calculate the p value, which

HERSCHEL KNAPP [continued]: will tell us if one group statistically significantly outperformed the other. [t Test-- Pretest Checklist] The t Test has three pretest criteria-- normality, n quota, and homogeneity of variance. [t Test-- Pretest Checklist] We'll check for normality now.

HERSCHEL KNAPP [continued]: The other two will be processed when we run the t Test. To check for normality, we need to order a histogram with normal curve for systolicBP for each group. We'll begin with Group 1, the group that got Drug A. Click Select Cases. Click If condition is satisfied.

HERSCHEL KNAPP [continued]: And click If. In the dialog box, enter Group = 1. Click Continue. And click OK. Now that only the records for Group 1 are active, we can order a histogram with a normal curve.

HERSCHEL KNAPP [continued]: Click Analyze, Descriptive Statistics, Frequencies. Move systolicBP to variables, click Charts, and select Histogram with normal curve. Click Continue. Click OK, and it'll process.

HERSCHEL KNAPP [continued]: The histogram for Group 1, Drug A, meets the normality criteria. Now we'll repeat this process for Group 2, Drug B. Click Select Cases and click If. In the dialog box, enter Group = 2.

HERSCHEL KNAPP [continued]: Click Continue. And click OK. Now that only the records for Group 2 are active, we can order a histogram with normal curve. Click Analyze, Descriptive Statistics, Frequencies. Notice that systolicBP is still in variables.

HERSCHEL KNAPP [continued]: Since the charts option hasn't been changed since our prior run, we don't need to revisit the Charts menu. Click OK and it'll process. The histogram for Group 2, Drug B, meets the normality criteria. [t Test-- Run] Before running the t Test, we need to select all of the records.

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SAGE Research Methods Video

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HERSCHEL KNAPP [continued]: The simplest way to do this is to click on the filter_$ variable and press the delete key. To run the t Test, click on Analyze, Compare Means, One-way ANOVA. SPSS does have a t Test menu, but the One-way ANOVA menu

HERSCHEL KNAPP [continued]: is easier to operate, produces the same results, and will lay the foundation for processing datasets in the ANOVA chapter. Move systolicBP to dependent list and move Group to factor. Click Options and click Descriptive and Homogeneity

HERSCHEL KNAPP [continued]: of variance test. Click Continue. Click OK. And it'll process. [t Test-- Results] We see that both groups have an n of at least 30, hence the n quota is satisfied. We also see that the Homogeneity of variance test

HERSCHEL KNAPP [continued]: returned a p value of 0.945. Since this is greater than 0.05, this indicates that there is no statistically significant difference in the variances between the groups. Hence, the Homogeneity of variance test is satisfied. Back to the descriptive table, notice that this table contains

HERSCHEL KNAPP [continued]: the means for each group. These figures will be useful when it comes to documenting the results. Finally, we see the results of the t Test. The p value is 0.014. Since this is less than or equal to point 0.05, this tells us that Drug A, with a mean of 120.37,

HERSCHEL KNAPP [continued]: statistically significantly outperformed Drug B, with a mean of 122.37, when it comes to lowering blood pressure. This concludes this video.

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SAGE Research Methods Video

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