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K B Gerald

Publications and source records attributed to K B Gerald.

16 recordsLinked to original sources
PubMed1991

Statistical analysis of categorical data.

This article has presented the most widely used techniques for analyzing categorical data. Data that are qualitative are naturally categorical. Even continuous (or measurement) data can be classified into categories (eg, ages can be grouped into above and below 40) and, hence, these procedures can be applied to a wide range of data. All of these statistical tests are classified as nonparametric statistics, although many statistical textbooks treat hypothesis testing of categorical data separately from the more common nonparametric methods. The most widely used nonparametric procedures will be reviewed in the next issue.

Data Interpretation, Statistical↗
PubMed1990

Analysis of bladder carcinoma by subsite. Cystoscopic location may have prognostic value.

Nine hundred fourteen cases of carcinoma of the urinary bladder registered from 1977 to 1988 with the Kansas state tumor registry were evaluated by subsite for differences in grade, histology, sex, age at diagnosis, and survival. Only initial occurrences of carcinoma were included. Carcinoma of the lateral walls accounted for 37.1%; the posterior wall, 17.9%; the trigone, 12.6%; the neck, 11.1%; the ureteric orifices, 9.8%; the dome, 7.7%; and the anterior wall, 3.8%. Malignant neoplasms occurring in the neck of the bladder had a significantly poorer prognosis by survival analysis (P less than 0.05). Malignancies of the dome were found to present as higher grade lesions (P = 0.00003), and carcinoma of the ureteric orifices and lateral walls tended to be of lower grade (P = 0.02 and P = 0.05, respectively). Carcinomas of the anterior wall and dome occurred in a more elderly population (mean ages, 75.6 and 73.9 years, respectively), and carcinomas of the trigone and ureteric orifices occurred in a younger group (mean ages, 68.3 and 67.5 years, respectively). On histologic evaluation the trigone gave rise to more squamous cell carcinoma than expected (P = 0.001, 325% of expected). No distribution difference was noted among subsites with respect to sex. These data show significant differences among subsites of the urinary bladder with regard to survival, grade, histology, and age at diagnosis.

Adenocarcinoma↗
PubMed1990

Review of the two sample t tests.

The t test is a valuable statistical manipulation of moderate strength to determine whether a significant difference exists between the means of two groups, either paired or unpaired. Generally, the larger the t value, the greater chance of its statistical significance. Sample size also will influence the point at which t becomes significant, that is, the larger the size of n, the smaller the t required to become significant. As the number of degrees of freedom becomes larger, a smaller t value is sufficient to reject the null hypothesis, and as variability increases, the true chance for significant difference decreases. It should be noted that a common error in the use of the t test occurs with excessive repetition of the test on the same dataset. A resultant type 1 error will be introduced that incorrectly concludes that significant differences have been demonstrated when, in fact, they have resulted not from significance but from repeated statistical application. In other words, if a .05 level of significance is used repeatedly on a dataset, the investigator is assuming that there is a 1 in 20 chance of finding a significant difference when there is no true difference between variables. It becomes obvious that if 20 repeated applications of the t test were performed, one would expect to find one significant difference by chance alone when no true difference exists. If more than 10 applications of the t test are being conducted on the same dataset, the investigator should lower the level of significance (.01) on each individual t test of the entire set so fewer null hypotheses are rejected. t Tests numbering 40 to 50 should have an alpha level of .005. An alternative approach would be to consult a statistician and use multivariate statistical procedures.

Analysis of Variance↗
PubMed1990

Common multiple comparison procedures.

With all the multiple comparison tests cited above, the logical question is, "Which procedure is best?" The answer to this question depends on whether an individual's decisions regarding differences should be conservative or nonconservative. The most powerful tests (LSD and Duncan's) are nonconservative (ie, more likely to detect a significant difference when it doesn't exist). Scheff's S method is so conservative that it is not useful when pairwise comparisons are desired and is more appropriate for "data dredging," that is, looking at contrasts suggested by the data. Waller and Duncan have proposed a k ratio rule to determine whether one needs to use a conservative rule (such as Tukey's) or a nonconservative rule (such as Fisher's LSD). In practice, the SNK procedure is commonly used because it is a good compromise between power and conservatism.

Humans↗
PubMed1986

Stability of 5-aminosalicylic acid suspension.

The stability of 5-aminosalicylic acid in a suspension prepared extemporaneously for administration by enema was studied. The suspension was prepared (tragacanth was the suspending agent) and then placed in 3-ounce amber glass prescription bottles; five bottles were stored at room temperature and five were refrigerated for 90 days. Using samples from each bottle, concentrations of 5-aminosalicylic acid were determined in triplicate by high-performance liquid chromatography at 0, 30, 60, and 90 days. Throughout the study period, all samples retained more than 90% of the day 0 concentration of 5-aminosalicylic acid. At each storage time, concentrations in samples stored at either room temperature or under refrigeration were not significantly different. In this extemporaneously prepared suspension, 5-aminosalicylic acid was stable for 90 days at room temperature and under refrigeration.

Aminosalicylic Acids↗
PubMed1985

Use of residence time moments in compartmental analysis.

Residence time moments, particularly mean residence times, can be very useful in the modeling and kinetic analysis of physiological systems. They are defined and illustrated, and their practical utility is then explored by comparing the model formulation based on these moments with three alternative formulations: component half-lives, compartmental model rate coefficients, and multiexponential model coefficients and exponents. The residence time moment formulation is shown to have several advantages: a smaller number of parameters are usually needed to describe a biological system; they have a clear physical interpretation; their statistical "power" to detect certain treatment differences is greater; and they are computationally simpler in many situations.

Animals↗
PubMed1978

A stochastic locomotor control model for the nurse shark, Ginglymostoma cirratum.

The locomotor behavior of the nurse shark (Ginglymostoma cirratum) is characterized by 17 variables (frequency and ratios of left, right, and total turns; their radians; straight paths (steps); distance travelled; and velocity) Within each of these variables there is an internal time dependency the structure of which was elaborated together with an improved statistical model predicting their behavior within 90% confidence limits. The model allows for the sensitive detection of subtle locomotor response to sensory stimulation as values of variables may exceed the established confidence limits within minutes after onset of the stimulus. The locomotor activity is well described by an autoregression time series model and can be predicted by only seven variables. Six of these form two independently operating clusters. The first one consists of: the number of right turns, the distance travelled and the mean velocity; the second one of: the mean size of right turns, of left turns, and of all turns. The same clustering is obtained independently by a cluster analysis of cross-sections of the seven time series. It is apparent that, among a total of 17 locomotor variables, seven behave as individually independent agents, presumably controlled by seven separate and independent centers. The output of each center can only be predicted by its own behavior. In spite of the individual of the seven variables, their internal structure is similar in important aspects which may result from control by a common command center. The shark locomotor model differs in important aspects from the previously constructed for the goldfish. The interdependence of the locomotor variables in both species may be related to the control mechanisms postulated by von Holst for the coordination of rhythmic fin movements in fishes. A locomotor control model for the nurse shark is proposed.

Animals↗
PubMedDate not supplied

Values held by nursing faculty and students in a university setting.

An ever-expanding wealth of life-preserving high technology and scientific knowledge, coupled with expanded autonomy of nurses, has created for them ethical and moral dilemmas. As society's values are changing, manifested by an accelerated crime rate, malfeasance in high places, and seeming social indifference, have nurses maintained their ethical equilibrium? This article reports the findings of a descriptive study that examined the professional and personal values of nursing faculty in a large midwestern school of nursing and compares them with those of generic students entering the program. Faculty demonstrated a significantly higher commitment to the American Association of College of Nursing professional value, human dignity, than to the values of equality (P less than .05) and esthetics (P less than .01). Also, there was a significantly higher commitment to altruism than esthetics (P less than .05). Results showed that entering students were more alike on personal values (Rokeach Values Survey) than different from the faculty who teach them.

Adult↗
PubMedDate not supplied

Diarrhea associated with tube feeding in mechanically ventilated critically ill patients.

This study was undertaken to determine the incidence and duration of diarrhea associated with tube feeding in critically ill adult patients who require mechanical ventilation. Of the 73 subjects studied, 63% had diarrhea associated with tube feeding. This incidence is higher than that reported from other studies of critically ill patients who were not mechanically ventilated. Multiple logistic regression analysis revealed that three variables (higher rates of infusion, greater tube-feeding osmolality, and change of tube-feeding product) were statistically significant predictors of diarrhea incidence. Antibiotic use and serum albumin levels were not predictors. In a stepwise multiple regression analysis, the duration of diarrhea was predicted by frequency of diarrhea, within the first 5 days of tube-feeding onset, tube-feeding product osmolality, and rate of tube-feeding infusion. Serum albumin levels and frequency of diarrhea beyond 6 days of tube-feeding onset did not predict duration of diarrhea. Higher osmolality and infusion rates of tube-feeding products did contribute to prediction of both incidence and duration of diarrhea.

Adolescent↗
PubMedDate not supplied

Cancer rates by county: how well does mortality relate to incidence?

The extent to which excess cancer mortality in a county is indicative of excess cancer incidence in the same county in the same time period was studied in white Iowa residents using routinely available 1973-1977 data. Evaluation consisted of population-weighted correlation analysis. The best correlations were obtained for cancers of the lung, pancreas, liver, stomach, brain (males), and kidney (males). These are the cancers for which excess mortality best indicates excess incidence. Correlations were low for prostate, female breast, and corpus uteri. The best indications of excess incidence are made for cancers with five year relative survival rates of 37.0 percent or less for males and 33.4 percent or less for females. Studies relating cancer mortality rates to occupational, environmental, or other demographic variables may be very misleading as to risk factors if the cancers selected have low correlations of incidence with mortality. Further development of the correlation model is recommended using data from all Surveillance, Epidemiology, and End Results Program counties for a ten-year period.

Epidemiologic Methods↗