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Commentary: Secondary Conditions and Life Satisfaction Among Polio Survivors
Rehabilitation Nursing Editorial Board Member
Two types of statistics are presented in Dr. Stuifbergen’s article—descriptive and inferential. The descriptive statistics present a concise summary of the characteristics of the study subjects; this type of statistic is also used to summarize the number of secondary conditions experienced and diagnosed by the subjects.
Descriptive statistics are organized by levels of data. Nominal data are frequency counts in categories such as gender or ethnicity. The frequency counts can also be expressed in percentages of the number of cases for each category. The researcher used percentages to summarize data as levels of education, marital status, employment status, and history of hospitalizations. An excellent use of descriptive statistics is presented in Table 1, which contains the percentages of secondary conditions organized by subject experiences, subject diagnoses, and a moderate to significant problem within the last 3 months. The researcher clearly answered study question one regarding the frequency of secondary conditions with descriptive statistics of percentages.
Interval-ratio level data are expressed concisely as the mean or average scores. This level represents data sets with equal intervals. The researcher used the mean (average) and standardized deviation (amount of variance in the scores) for the age of subjects, age at initial polio diagnosis, average number of secondary conditions experienced, and secondary conditions diagnosed.
The second category of statistics used in the article is inferential, which allow the researcher to generalize findings from a sample group to a population of like subjects. The researcher used multiple Pearson correlations to analyze the relationship of variables by age, level of education, age at time of polio diagnosis, age at time of post-polio syndrome diagnosis, decrease in normal activities, use of assistive devices, and life satisfaction with the variables of secondary conditions experienced or diagnosed and extent of difficulty in the last 3 months. The correlation can be expressed as a positive, negative, or no correlation. Correlations range from –1 (negative or opposite relationship) to +1 (positive relationship). Correlations of zero mean there are no relationships of the variables.
The appropriate inferential statistic is based on the study questions or hypotheses, study design, and level of data. The researcher developed study question two involving the association of demographic factors and polio-related factors with secondary conditions. The third study question focuses on the relationship between secondary conditions and life satisfaction. Both terms of relationship and association were used with correlation statistical analysis (Pearson’s product-moment correlation) to investigate relationships between two variables. The study design was a descriptive correlational design. The level of data within the study was of an interval level appropriate for the Pearson correlation. Time, as with age and years of education, was considered an interval item. The percentage scores of those with post-polio syndrome and decreased ability with activities were also considered interval, because there is a set interval in percentage. The number of secondary conditions experienced or diagnosed and the number of assistance devices were also considered interval. The extent-of-difficulty and life satisfaction data were collected by using questionnaires with 6- or 4-point scales. The total scores of both the Quality of Life Index and the modified Tate questionnaire were considered interval-level data. Study questions two and three, the study design, and the interval level of data indicate the correct correlational statistic was used to analzze study data.
The correlations of secondary conditions and diagnoses are clearly presented in Table 2. The levels of significance are displayed as p < .01 and p < .001, which indicated a strong relationship of two variables. Study question two was answered in Table 2 with the correlations of age, post-polio diagnosis, number of assistive devices, and the ability to carry out activities associated with secondary conditions. The years-of-education variable was not found to have a significant correlation with secondary conditions. Question three was answered; life satisfaction was significantly correlated with secondary conditions.
In summary, the researcher used descriptive statistics of percentages, means, and standard deviations to concisely organize and report data sets. The researcher correctly used the Pearson product-moment correlation to investigate the multiple sets of two variables within the study and found many significant correlations with the variables.