Every analysis should begin by describing and graphing the data. In the case “Nurses’ Perception of Evidence-based Practice: Assessing the Current Culture” the demographic characteristics for all nurses were summarized with descriptive statistics as shown in Figure 1.5. Since we are interested in differences by organizational level we will summarize the nurses’ demographic characteristics by organizational level using Tabulate. Drag and drop the demographic characteristics into the drop zone for rows and then drag and drop N and Column % into the drop zone for columns. Now drag Org level to the top of the N and Column % cells. The complete table is shown in Figure 3.3 JMP Tabulate Output for Nurse Demographics by Organizational Level.

When expressing percentages in a table, there are three choices for how the percentage can be calculated: as a percent of total number of observations, as a percent of the column totals, or as a percent of the row totals. The choice of which percentage to display depends on the analysis objective. In this case we are interested in comparing by organizational level and since that is the column variable in the table, column % is selected. Comparing the demographic characteristics between nurse professionals and leaders we see that:

Understanding the demographic differences between the two groups of nurses is valuable when interpreting the differences in their perceptions of EBP.

We will summarize the responses to the two survey questions of interest first overall and then by organization level using Analyze > Consumer Research > Categorical. Select Simple for the Response Roles and check the box for Count Missing Responses.

Figure 3.4 Completed Categorical Dialog for Survey Question "All of the practice changes so far have been practical and fit well with the workflow of the unit” shows the completed Categorical dialog.

Figure 3.5 Categorical Response Analysis of Two Survey Questions shows a descriptive analysis for all respondents combined for the two survey questions “All of the practice changes so far have been practical and fit well with the workflow of the unit” and “Evidence based practice does not take into account the limitations of my practice setting” in both tabular and graphical form.

The tables give the count of missing responses and their percentage of the total responses. Alternatively, the missing values can be omitted by leaving "Count Missing Responses" unchecked in the Categorical dialog.

Both questions show a similar pattern of agreement and have the same number of nurses who did not offer a rating. Notice that the question about unit workflow is phrased positively and the question about practice setting is phrased in the negative. In general, the nurses are more positive about EBP with respect to practicality and workflow but view EBP more negatively in terms of practice setting. Best practice in survey design favors phrasing all questions positively. Mixing questions that are phrased both positively and negatively can be confusing to the respondent and may lead to unintended response choices.

Figure 3.6 Categorical Response Analysis of Two Survey Questions by Organizational Level shows survey responses to the two questions by organization level. Again, you can obtain this output by selecting Analyze>Consumer Research>Categorical and enter the column Org Level into the X grouping category.

For the rating question on EBP practicality and workflow the nurse professionals had a higher level of neutral response than did the leaders who generally are in more agreement with the proposition. The leaders generally felt that EBP took practice settings limitations into account while nurse professionals did not. Descriptive analysis allows you to observe differences between the organizational levels but does not tell you if these differences are statistically significant. A test of hypothesis is needed to determine statistically significant differences.

Fit Y by X is the appropriate platform to conduct a chi-square test for independence. For this analysis, the column containing the responses to a survey question is the Y and the variable Org Level is the X, as shown in Figure 3.7 Completed Fit Y by X Dialog. .

To show the percentages on the mosaic plot, right click over one of the panels and select Cell Labeling > Show Percents. Figure 3.8 Chi-square Analysis for the Practicality and Workflow Question shows the JMP output for the practicality and workflow question.

The large mosaic plot shows the proportion of responses in each rating category by each of the organization levels. The small mosaic plot to the right shows the proportion of responses in each rating category for both nurse professionals and leaders combined. This represents the null hypothesis of independence, i.e., both organization levels have the same proportion in each rating category. If the mosaic plots by organization level are similar, then this is consistent with the null hypothesis of independence. Less similarity between the mosaic plots for the two organization levels suggests the data is not consistent with the null hypothesis.

The contingency table displays the observed counts and the counts that would be expected if the pattern of agreement is independent of the organization level. The red triangle menu offers a variety of options that can be shown in the contingency table, including both conditional and unconditional relative frequencies. The chi-squared test for independence compares the observed frequency (Count in the JMP contingency table) to the expected frequency.

We can’t establish statistical significance through visual comparison of graphs or comparing the counts in a contingency table. The chi-square test statistic and the associated p-value (Prob>ChiSq) are found in the Tests section. However, the warning at the bottom of the JMP output indicates that the chi-square assumption for the minimum number of cells with expected counts greater than 5 is not satisfied. You can remedy this problem by combining some of the response columns. In this case we can reduce the 5-point Likert scale to a 3-point scale by combining the strongly disagree and disagree categories and the strongly agree and agree categories. JMP’s Recode feature provides an easy means to create a column containing the levels disagreement, neutral, and agreement. Rerunning the chi-square analysis yields the results in Figure 3.9 Chi-square Analysis for the Practicality and Workflow Question with a 3-point Scale .

Note that the chi-square assumption is now satisfied and we can safely use the p-value from the Pearson chi-square test (0.0452) which tells us that at the 5% significance level the perception of EBP with respect to practicality and workflow depends on whether you are a leader or a nurse professional. P-values that are less than the chosen significance level cause a rejection of the null hypothesis. A p-value is the likelihood of obtaining the sample outcome, or something more extreme, assuming the null hypothesis is true. Figure 3.10 Categorical Response Analysis of the Practicality and Workflow Question by Organizational Level shows the distribution of the response for the two organization levels.

The leaders show a slight majority in agreement while the nurse professionals most frequently respond with neutral and have slightly more in agreement than in disagreement. So for the proposition “All of the practice changes so far have been practical and fit well with the workflow of the unit,” the nurse professionals and nurse leaders differ in their patterns of agreement.

Finally, we consider the survey question “Evidence based practice does not take into account the limitations of my practice setting.” The chi-square analysis is shown in Figure 3.11 Chi-square Analysis for the Limitations of Practice Setting Question.

For this survey question, the chi-square assumption for the minimum number of cells with counts of at least five is satisfied and the p-value of 0.0180 from the Pearson test indicates that there is a statistically significant difference at the 5% level in how leaders and nurse professionals view EBP in relation to the limitations of their practice setting. Figure 3.5 Categorical Response Analysis of Two Survey Questions shows the differences in the support for the proposition with leaders generally finding EBP is consistent with practice setting limitations while the nurse professionals do not.

Finally, we address the assumption of independence between survey respondents. This assumption is best satisfied during the design and administration of the survey. For example, sending the survey link to a respondent’s home email rather than their work email may reduce the influence of co-workers.