Questions to Be Graded EXERCISE 26 Follow your instructor ’ s directions to submit your answers to the following questions for grading. Your instructor may ask you to write your answers below and submit them as a hard copy for grading. Alternatively, your

Questions to Be Graded EXERCISE 26Follow your instructor ’ s directions to submit your answers to the following questions for grading.Your instructor may ask you to write your answers below and submit them as a hard copy forgrading. Alternatively, your instructor may ask you to use the space below for notes and submit youranswers online at http://evolve.elsevier.com/Grove/Statistics/ under “Questions to Be Graded.”Name: _______________________________________________________ Class: _____________________Date: ___________________________________________________________________________________1. Plot the frequency distribution for “Age at Enrollment” by hand or by using SPSS.2. How would you characterize the skewness of the distribution in Question 1—positively skewed,negatively skewed, or approximately normal? Provide a rationale for your answer.3. Compare the original skewness statistic and Shapiro-Wilk statistic with those of the smallerdataset ( n = 15) for the variable “Age at First Arrest.” How did the statistics change, and howwould you explain these differences?4. Plot the frequency distribution for “Years of Education” by hand or by using SPSS.290 EXERCISE 26 • Determining the Normality of a DistributionCopyright © 2017, Elsevier Inc. All rights reserved.5. How would you characterize the kurtosis of the distribution in Question 4—leptokurtic, mesokurtic,or platykurtic? Provide a rationale for your answer.6. What is the skewness statistic for “Age at Enrollment”? How would you characterize the magnitudeof the skewness statistic for “Age at Enrollment”?7. What is the kurtosis statistic for “Years of Education”? How would you characterize the magnitudeof the kurtosis statistic for “Years of Education”?8. Using SPSS, compute the Shapiro-Wilk statistic for “Number of Times Fired from Job.” Whatwould you conclude from the results?9. In the SPSS output table titled “Tests of Normality,” the Shapiro-Wilk statistic is reported alongwith the Kolmogorov-Smirnov statistic. Why is the Kolmogorov-Smirnov statistic inappropriateto report for these example data?10. How would you explain the skewness statistic for a particular frequency distribution being lowand the Shapiro-Wilk statistic still being signifi cant at p < 0.05?Copyright © 2017, Elsevier Inc. All rights reserved. 291Calculating Descriptive StatisticsThere are two major classes of statistics: descriptive statistics and inferential statistics.Descriptive statistics are computed to reveal characteristics of the sample data set and todescribe study variables. Inferential statistics are computed to gain information abouteffects and associations in the population being studied. For some types of studies,descriptive statistics will be the only approach to analysis of the data. For other studies,descriptive statistics are the fi rst step in the data analysis process, to be followed by inferentialstatistics. For all studies that involve numerical data, descriptive statistics arecrucial in understanding the fundamental properties of the variables being studied. Exercise27 focuses only on descriptive statistics and will illustrate the most common descriptivestatistics computed in nursing research and provide examples using actual clinicaldata from empirical publications.MEASURES OF CENTRAL TENDENCYA measure of central tendency is a statistic that represents the center or middle of afrequency distribution. The three measures of central tendency commonly used in nursingresearch are the mode, median ( MD ), and mean ( X ). The mean is the arithmetic averageof all of a variable ’ s values. The median is the exact middle value (or the average of themiddle two values if there is an even number of observations). The mode is the mostcommonly occurring value or values (see Exercise 8 ).The following data have been collected from veterans with rheumatoid arthritis ( Tran,Hooker, Cipher, & Reimold, 2009 ). The values in Table 27-1 were extracted from a largersample of veterans who had a history of biologic medication use (e.g., infl iximab [Remicade],etanercept [Enbrel]). Table 27-1 contains data collected from 10 veterans who hadstopped taking biologic medications, and the variable represents the number of years thateach veteran had taken the medication before stopping.Because the number of study subjects represented below is 10, the correct statisticalnotation to refl ect that number is:n 10Note that the n is lowercase, because we are referring to a sample of veterans. If thedata being presented represented the entire population of veterans, the correct notationis the uppercase N. Because most nursing research is conducted using samples, not populations,all formulas in the subsequent exercises will incorporate the sample notation, n.ModeThe mode is the numerical value or score that occurs with the greatest frequency; it doesnot necessarily indicate the center of the data set. The data in Table 27-1 contain twoEXERCISE27