An example of how to report is shared below. After discussing the scale i-e their Number of items in the scale, scale for response you can describe the reliability of the instrument. It is normally reported in the methodology section where instrument are discussed. If any of the values in this column are higher than the final alpha value, you may want to consider removing this item from the scale. Compare these values in the column headed Alpha if Item Deleted with the alpha value obtained. In the column headed Alpha if Item Deleted, the impact of removing each item from the scale is given. 7) and you have checked for reverse items that might not have been entered properly, It would be a good idea to consider removing items with low item-total correlations. If scale’s overall Cronbach’s alpha istoo low (e.g. 3) here indicate that the item is measuring somethingdifferent from the scale as a whole. The Corrected Item-Total Correlation column in the Item-Total Statistics table provides an indication of the degree to which each item correlates with thetotal score. The overall reliability of the scale can be improved by following a few simple guidelines: The presence of negative values could indicate that some of the items have not been correctly reverse scored. All values should be positive, indicating that the items are measuring the same underlying characteristic and account for the same construct. In this particular case both are correct, none of the cases are excluded and the number is items are 4 which are correct.Ĭheck the Inter-Item Correlation Matrix for negative values. It shows if removing a certain item will improve the overall reliability of the scale, however in this particular case the Cronbach’s alpha won’t improve by removing any of the items.Ĭheck that the number of cases is correct (in the Case Processing Summary table) and that the number of items is correct (in the Reliability Statistics table). The last column labeled Cronbach’s Alpha if Item Deletedcan help improve the reliability of the scale. The fourth column in this table, titled Corrected Item-Total Correlationgives an indication of the degree to which each item correlates with the composite score for the scale. The table titled Item Statisticsgives item-wise mean and standard deviation values. SPSS also provides us with descriptive statistics.
This recommends that the scale is consistent and highly reliable. For our scale of Training Needs AnalysisCronbach’s alpha value reported to be 0.900.
The second table of Reliability Statisticsis the table of interest, it gives the value of the Cronbach’s alpha and the number of items selected for the scale. The first table shows the Case Processing Summary, showing the total number of valid cases and if any data was excluded from the analysis. Click on Continue to return to the main dialog box then click on OK to run the analysis. Check Item, Scale, and Scale if item deleted from Descriptive Statistics group box. Click on the Statistics button which will open a dialog box. Add the selected list of variables to items list box.ĥ. For this example we will select TNA1 to TNA4 related to scale Training Needs Analysis (Once Added your Dialog box should resemble the one in figure 8.1).Ĥ. Select only the variables for One Construct (Scale) at a time. Select the items whose reliability is to be assessed from the variable list box. You will see Reliability Analysis dialog box.ģ. Choose Analyze → Scale → Reliability AnalysisĢ. Procedure for checking the reliability of a scaleġ. Now when you enter the response for item 4 into SPSS, you need to reverse the entry, for instance if the respondent has said 5, you will enter 1 into SPSS, similarly 4 will be exchange with 2 and vice versa. We can see that item 4 is in reverse order, it is negative while all other questions are positive.
For instance we have a Scale named “Work Morale” having the following questions answered on likert scale (1 – Strongly Disagree to 5 – Strongly Agree)Įveryone around here looks forward to come to work. If your scale contains some items that are negatively worded (common in psychological measures), these need to be ‘reversed’ before checking reliability. Reliability is normally reported under the head of instrumentation in the methodology section. scales with fewer than ten items) it is common to find quite low Cronbach’s values (e.g.5). Cronbach’s alpha values are quite sensitive to the number of items in the scale.