Questionnaires sample sizes

In Greece, a case-control study was conducted to investigate the incidence of liver cancer by estimating the consumption of six types of flavonoids with a semiquantitative questionnaire on the frequency of foods. The intake of flavones was inversely associated with hepatocellular carcinoma, irrespective of its etiology (viral or nonviral). With respect to cholangiocarcinoma, an inverse association with the consumption of flavan-3-ols, anthocyanidins, and total flavonoids studied was found. However, this last result should be viewed with caution because of the small sample size, due to the fact that this is a rare type of cancer (Lagiou and others 2008). 

A third report is Intended to provide a final evaluation of the chemicals tested. Volume 3 will report on the current health status of the soldier participants on the basis of a recent questionnaire and Interpret Its impact on the conclusions reported in Volumes 1 and 2. The followup questionnaire to volunteer subjects may add descriptive data, but, because of the limited sample size, it Is unlikely to provide evidence of a cause-and-effect relation between exposure to these chemicals and development of delayed disease. 

As with any form of sample-based research, it is important to know in advance how much data (completed questionnaires) will be required. We can calculate a necessary sample size using the approaches described earlier in this book. We just need to identify the primary question, determine what statistical analysis will be used to answer it and then perform a sample size calculation in the normal way. 

An appropriate sample size - number of completed questionnaires - should be calculated (as described in earlier chapters). It is not satisfactory to attempt to compensate for a low return rate by simply increasing the numbers sent out. That tactic risks a biased return. 

Patients with migraine who use daily codeine or other opioids can be more susceptible to chronic daily headaches this is evident in opiate overuse. In a pilot questionnaire study of 32 patients who used codeine or other opioids for control of their bowel motility after colectomy, chronic daily headaches occurred in those who were misusing opioids, but only if they had pre-existing migraine (3). The study had significant limitations, including the small sample size, diagnosis by means of a mailed questionnaire, a short duration of overuse of opioids, and the fact that it was uncontrolled. 

The study collected 224 cases of the domestic typical foundation pit accidents mainly by referring to relevant literature and issuing questionnaires, yet it could not cover all cases limited to all aspects of objective reason, as shown in Table 1 (due to the limited space, not enumerate). From the viewpoint of statistics, the greater the sample size, the more reliable the analysis results are. And case collection is a continuous process, therefore, in the follow-up work we will enrich the cases via dilferent approaches, timely update and optimize the analysis result. 

One means of gathering data for monitor indicators is patient safety culture questionnaires. We have developed a patient safety culture questionnaire, TUKU, that measures employees perceptions of the organisational functions depicted in Table 9.4 as well as employees psychological states, such as sense of control and worry about patient safety (Reiman et al. 2013). In one hospital, the results of the questionnaire were compared with the ratio of patient safety incidents at the hospital s 40 units 16 months after the safety culture questionnaire was administered. The results, which must be treated with caution due to the small sample size, indicated that perceptions of work process management , work conditions management . 

This study used a quasi-experimental design with quantitative data (Anderson, 2000 CresweU, 2003) that used two previously designed questionnaires to solicit information related to several affective factors from second-year college chemistry students who were involved in a problem-based learning (PEL) chemistry laboratory corrrse. In order to make comparisons in particular instances, information was also solicited from a group of students enrolled in a traditional laboratory course that involved carrying out specific laboratory activities based on instructions that were provided. With the small sample size and the likelihood of non-normal distribution, any differences between the treatment and comparison groups and between pre- and posttests were analyzed with nonparametric statistics. 

On occasion, such a survey may indicate the need for a more formal epidemiological study. Skin complaints may, for example, be widespread but unusually hard to explain. Such investigations should never be undertaken by clinicians without previous epidemiological and statistical consultation. Coenraads and Nater (1987) have published a useful introduction to the problems that may arise, including true prevalence estimation, bias, confounding variables and sample size. Questions of disease definition and inter-observer variability are not necessarily familiar to clinicians, who may therefore need to seek epidemiological advice at the earliest opportunity. Questionnaires are frequently designed that ask for far more detail than can possibly be usefully analysed statistically, and they should always be piloted first in order to achieve validity. 

To test these two alternative explanations, I conduct two-step regression analj es 1 use lead userness and control variables in a baseline model that is then augmented by functional affiliation and job satisfoction, respectively. Note that the sample size is smaller in the case of job satisfaction [n=97], the reason being that questions on job satisfaction were optional for firms 2, 3 and 4, and were not included at all in the questionnaire used in firm 1. As we will see, my results do not lend empirical support to either of the two alternative explanations. 

Finally, two earlier dietary studies are worth mentioning. Vollset and Bjelke (1983) reported an inverse association of vitamin C index with cerebrovascular disease mortality rates in a study of 16,713 postal workers over 11 years of followup. Vitamin C index was estimated from fruit and vegetable intake obtained from periodic food questionnaires. In a prospective cohort of 1462 Swedish women, estimates of vitamin C intake from a 24-hr recall dietary history were not correlated with CVD mortality after 12 years of follow-up after controlling for age (Lapidus et al.y 1986). Dietary intake by 24-hr recall may correlate poorly with estimates of average consumption of micronutrients assessed by food diary or food frequency questionnaire. In addition, statistical power to detect small to moderate associations may be lacking in this study, given the sample size. 

This study has several hmitations. Firstly, the sample size is sufficient but a sample with more cases could have made the results more valid. Therefore, the results have to be evaluated in further research. There are also limitations related to the measures that were used. Due to restrictions on the length of the questionnaire the number of items was limited. This aspect probably reduced construct validity to some degree compared to more complete scales. The non-existence of appropriate measures also made it necessary to develop new items. Although the scales were developed on the theoretical and empirical basis the scales and indices need modification and refinement in future research. 

In this study, the researchers focus on SMEs in the manufacturing sector, the sampled group size was 100 SMEs, and data were collected by quota sampling. With the above sampling groups, a questionnaire was used as a tool for data collection to create a questionnaire checklist by smdying twenty-four variables under all the five performance measurement perspectives (quality, time, finance, and customer satisfaction) for performance measurement of SMEs in the manufacturing sector in the province. 

A Chi-square test is conducted to check non-response bias. The results (see Table 7.2) show that there is no significant difference between the first-wave and second/third-wave respondents by aU three categories (i.e., SIC code, firm size, and job title) at the level of 0.1. It exhibits that received questionnaires from respondents represent an unbiased sample. 

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