# Descriptive Statistics

**Week 4 Descriptive Statistics**

**To prepare:**

Review the Statistics and Data Analysis for Nursing Research chapters assigned in this week’s Learning Resources. Pay close attention to the examples presented, as they provide information that will be useful when you complete the software exercise this week. You may also wish to review the Research Methods for Evidence-Based Practice video resources to familiarize yourself with the software.

Refer to the Week 4 Descriptive Statistics Assignment page and follow the directions to calculate descriptive statistics for the data provided using SPSS software. Download and save the Polit2SetA.sav data set. You will open the data file in SPSS.

Compare your data output against the tables presented in the Week 4 Descriptive Statistics SPSS Output document. This will enable you to become comfortable with defining variables, entering data, and creating tables and graphs.

Formulate an initial interpretation of the meaning or implication of your calculations.

To complete:

**Complete the Part I, Part II, and Part III s**teps and Assignment as outlined in the Week 4 Descriptive Statistics Assignment page.

**Part I**

Using the Polit2SetA data set, run descriptive statistics on the following variables: respondent’s age (*age*) and highest school grade completed (*higrade*). Create a frequency distribution for the variables: race and ethnicity (*racethn*) and currently employed (*worknow*). Create a table (in APA format) summarizing the results, using the below table shell as a model. Write a paragraph summarizing the information in the table.

Table 1. Demographic Data (*N* = 30)

*n* % M (SD)

Age (in years) 30 15(2.4)

Highest School Grade Completed 29 11(1.2)

Race and Ethnicity

Black, Not Hispanic 14 (46.67)

Hispanic 8 (26.67)

White, Not Hispanic 6 (20.0)

Other 2 (6.66)

Currently Employed

Yes 27 (90)

No 3 (10)

*Note.* Differences in sample size are due to missing data.

Follow these steps when using SPSS:

1. Open Polit2SetA data set.

2. Click on **Analyze,** then click on **Descriptives Statistics**, then **Descriptives**.

3. Click on the first continuous variable you wish to obtain descriptives for (respondent’s age), and then click on the arrow button and move it into the Variables box. Then click on **highest school grade completed **and then click on the arrow button and move it into the Variables box.

4. Click on the **Options **button in the upper-right corner. Click on **mean**, **standard deviation**, **minimum**, **maximum**, and **skewness**.

5. Click on **Continue **and then click on **OK**.

To run the frequency distribution in SPSS, do the following:

1. Click on **Analyze**, then click on **Descriptive Statistics**, then **Frequencies**.

2. Click on the first categorical variable you wish to obtain a frequency for (race and ethnicity), and then click on the arrow button and move it into the Variables box. Then click on **currently employed,** and then click on the arrow button and move it into the Variables box. Click on the **Statistics** button in the upper-right corner, then in the Dispersion box click on **Minimum and Maximum**.

3. Click on **Continue **and then click on **OK**.

**Assignment:** Create a table (in APA format) summarizing the results, using the below table shell as a model. Write a paragraph summarizing the information in the table.

**Part II**

For the variables respondent’s age (*age*) and highest school grade completed (*higrade*) create a histogram with a normal curve displayed over the histogram.

To create a histogram for respondent’s age in SPSS, do the following:

1. Click on **Graphs**, then on **Legacy Dialogs**, then **Histogram**.

2. Click on the variable **respondent’s age** and then click on the arrow button and move it into the Variables box. Click on the **Display Normal Curve** button, which is right below the Variables box.

3. Click on **OK**.

To create a histogram for highest school grade completed in SPSS, do the following:

1. Click on **Graphs**, then on **Legacy Dialogs**, then **Histogram**.

2. Click on **respondent’s age **in the Variable box and click the arrow to move it back to the box on the left that contains all the variables.

3. Click on the variable **highest school grade completed **and then click the arrow button and move it into the Variables box. The **Display Normal Curve** button should alredy be on.

4. Click on **OK**.

**Assignment:** Using the data obtained when you ran the descriptives and the histograms, determine whether the data skewed. If so, is it a positive or negative skew?

**Part III**

Using the Polit2SetA data set, run descriptive statistics on the variable “Family Income Prior Month, all sources” (Income).

Follow these steps when using SPSS:

1. Click on **Analyze**, then click on **Descriptives Statistics**, then **Descriptives**.

2. Click on **Family Income Prior Month, all sources**, and then click on the arrow button and move it into the Variables box.

3. Click on the **Options **button in the upper-right corner. Click on **mean**, **standard deviation**, **minimum**, **maximum**, **S.E. Mean **(standard error of the mean), and **skewness**.

4. Click on **Continue** and then click on **OK**.

**Assignment:** Using the descriptive statistics for Family Income Prior Month, all sources (Income), answer the following questions:

1. What is the mean income in this sample?

2. What is the standard deviation?

3. What is the standard error of the mean?

4. Compute a 95% confidence interval around the mean. (Use 1.96 for the 95% CI and get the standard error from the descriptive statistics table). The formula is as follows:

95% CI = [mean ± (1.96 ´ SE)]

5. Compute a 99% confidence interval around the mean. (Use 2.58 for the 99% CI and get the standard error from the descriptive statistics table). The formula is as follows:

99% CI = [mean ± (2.58 ´ SE)]

6. Which interval is wider? Explain.

Review the corresponding Week 4 Descriptive Statistics Exercises SPSS Output document that has the SPSS output for the above problems. Compare your output with the output in the file.

REFERENCES

aureate Education, Inc. (Executive Producer). (2011). *Research methods for evidence-based practice: Quantitative research: Data analysis.* Baltimore, MD: Author.

Polit, D. (2010). *Statistics and data analysis for nursing research* (2nd ed.). Upper Saddle River, NJ: Pearson Education Inc.

· Chapter 1, “Introduction to Data Analysis in an Evidence-Based Practice Environment”

Week 4 Descriptive Statistics Exercises SPSS Output

Part I

Respondent’s Age Descriptive Statistics

N Minimum Maximum Mean Std. Deviation Skewness Statistic Statistic Statistic Statistic Statistic Statistic Std. Error

Respondent’s age at time of

interview

1000 19.378 49.430 36.63733 6.198741 -.374 .077

Valid N (listwise) 1000

Highest School Grade Completed

Descriptive Statistics

N Minimum Maximum Mean Std. Deviation Skewness Statistic Statistic Statistic Statistic Statistic Statistic Std. Error

Highest school grade

completed

989 1 16 11.28 1.561 -.727 .078

Valid N (listwise) 989

Race and Ethnicity

Race/ethnicity

Frequency Percent Valid Percent

Cumulative

Percent

Valid Black, not Hispanic 803 80.3 80.5 80.5

Hispanic 128 12.8 12.8 93.3

White, not Hispanic 53 5.3 5.3 98.6

Other 14 1.4 1.4 100.0

Total 998 99.8 100.0 Missing Refused 1 .1

DK 1 .1 Total 2 .2

Total 1000 100.0

Currently Employed

Currently employed?

Frequency Percent Valid Percent

Cumulative

Percent

Valid No 546 54.6 54.7 54.7

Yes 452 45.2 45.3 100.0

Total 998 99.8 100.0 Missing System 2 .2 Total 1000 100.0

Part II

Part III Family Income

Descriptive Statistics

N Minimum Maximum Mean Std. Deviation Skewness Statistic Statistic Statistic Statistic Std. Error Statistic Statistic Std. Error

Family income prior month,

all sources

895 $0 $6,593 $1,172.59 $26.345 $788.153 2.030 .082

Valid N (listwise) 895