### 统计代写|生物统计代写biostatistics代考|DESCRIBING POPULATIONS

statistics-lab™ 为您的留学生涯保驾护航 在代写生物统计biostatistics方面已经树立了自己的口碑, 保证靠谱, 高质且原创的统计Statistics代写服务。我们的专家在代写生物统计biostatistics代写方面经验极为丰富，各种生物统计biostatistics相关的作业也就用不着说。

• Statistical Inference 统计推断
• Statistical Computing 统计计算
• (Generalized) Linear Models 广义线性模型
• Statistical Machine Learning 统计机器学习
• Longitudinal Data Analysis 纵向数据分析
• Foundations of Data Science 数据科学基础

## 统计代写|生物统计代写biostatistics代考|The Phases of a Clinical Trial

Clinical research is often conducted in a series of steps, called phases. Because a new drug, medicine, or treatment must be safe, effective, and manufactured at a consistent quality, a series of rigorous clinical trials are usually required before the drug, medicine, or treatment can be made available to the general public. In the United States the FDA regulates and oversees the testing and approval of new drugs as well as dietary supplements, cosmetics, medical devices, blood products, and the content of health claims on food labels. The approval of a new drug by the FDA requires extensive testing and evaluation of the drug through a series of four clinical trials, which are referred to as phase $I, I I, I I I$, and $I V$ trials.
Each of the four phases is designed with a different purpose and to provide the necessary information to help biomedical researchers answer several different questions about

a new drug, treatment, or biomedical procedure. After a clinical trial is completed, the researchers use biostatistical methods to analyze the data collected during the trial and make decisions and draw conclusions about the meaning of their findings and whether further studies are needed. After each phase in the study of a new drug or treatment, the research team must decide whether to proceed to the next phase or stop the investigation of the drug/treatment. Formal approval of a new drug or biomedical procedure generally cannot be made until a phase III trial is completed and there is strong evidence that the drug/treatment is safe and effective.

The purpose of a phase $I$ clinical trial is to investigate the safety, efficacy, and side effects of a new drug or treatment. Phase I trials usually involve a small number of subjects and take place at a single or only a few different locations. In a drug trial, the goal of a phase I trial is often to investigate the metabolic and pharmacologic actions of the drug, the efficacy of the drug, and the side effects associated with different dosages of the drug. Phase I drug trials are also referred to as dose finding trials.

## 统计代写|生物统计代写biostatistics代考|POPULATIONS AND VARIABLES

In a properly designed biomedical research study, a well-defined target population and a particular set of research questions dictate the variables that should be measured on the units being studied in the research project. In most research problems, there are many variables

that must be measured on each unit in the population. The outcome variables that are of primary interest are called the response variables, and the variables that are believed to explain the response variables are called the explanatory variables or predictor variables. For example, in a clinical trial designed to study the efficacy of a specialized treatment designed to reduce the size of a malignant tumor, the following explanatory variables might be recorded for each patient in the study: age, gender, race, weight, height, blood type, blood pressure, and oxygen uptake. The response variable in this study might be change in the size of the tumor.

Variables come in a variety of different types; however, each variable can be classified as being either quantitative or qualitative in nature. A variable that takes on only numeric values is a quantitative variable, and a variable that takes on non-numeric values is called a qualitative variable or a categorical variable. Note that a variable is a quantitative or qualitative variable based on the possible values the variable can take on.
Example $2.1$
In a study of obesity in the population of children aged 10 or less in the United States, some possible quantitative variables that might be measured include age, height, weight, heart rate, body mass index, and percent body fat; some qualitative variables that might be measured on this population include gender, eye color, race, and blood type. A likely choice for the response variable in this study would be the qualitative variable Obese defined by
$$\text { Obese }= \begin{cases}\text { Yes } & \text { for a body mass index of }>30 \ \text { No } & \text { for a body mass index of } \leq 30\end{cases}$$

## 统计代写|生物统计代写biostatistics代考|Qualitative Variables

Qualitative variables take on nonnumeric values and are usually used to represent a distinct quality of a population unit. When the possible values of a qualitative variable have no intrinsic ordering, the variable is called a nominal variable; when there is a natural ordering of the possible values of the variable, then the variable is called an ordinal variable. An example of a nominal variable is Blood Type where the standard values for blood type are $\mathrm{A}, \mathrm{B}, \mathrm{AB}$, and $\mathrm{O}$. Clearly, there is no intrinsic ordering of these blood types, and hence, Blood Type is a nominal variable. An example of an ordinal variable is the variable Pain where a subject is asked to describe their pain verbally as

• No pain,
• Mild pain,
• Discomforting pain,
• Distressing pain,
• Intense pain,
• Excruciating pain.
In this case, since the verbal descriptions describe increasing levels of pain, there is a clear ordering of the possible values of the variable Pain levels, and therefore, Pain is an ordinal qualitative variable.
Example 2.2
In the Framingham Heart Study of coronary heart disease, the following two nominal qualitative variables were recorded:
$$\text { Smokes }=\left{\begin{array}{l} \text { Yes } \ \text { No } \end{array}\right.$$
• and
• $$• \text { Diabetes }=\left{\begin{array}{l} • \text { Yes } \ • \text { No } • \end{array}\right. •$$

## 统计代写|生物统计代写biostatistics代考|POPULATIONS AND VARIABLES

肥胖 ={ 是的  对于体重指数 >30  不  对于体重指数 ≤30

## 统计代写|生物统计代写biostatistics代考|Qualitative Variables

• 不痛，
• 轻微的疼痛，
• 令人不适的疼痛，
• 让人心疼的痛，
• 剧烈的疼痛，
• 难以忍受的疼痛。
在这种情况下，由于口头描述描述了疼痛程度的增加，因此变量疼痛水平的可能值有一个明确的顺序，因此，疼痛是一个有序的定性变量。
例 2.2
在冠心病的弗雷明汉心脏研究中，记录了以下两个名义上的定性变量：
$$\text { Smokes }=\left{ 是的 不 \正确的。$$
• $$• \text { 糖尿病 }=\left{\begin{array}{l} • \文本{是} \ • \文本{没有} • \end{数组}\对。 •$$

## 有限元方法代写

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## MATLAB代写

MATLAB 是一种用于技术计算的高性能语言。它将计算、可视化和编程集成在一个易于使用的环境中，其中问题和解决方案以熟悉的数学符号表示。典型用途包括：数学和计算算法开发建模、仿真和原型制作数据分析、探索和可视化科学和工程图形应用程序开发，包括图形用户界面构建MATLAB 是一个交互式系统，其基本数据元素是一个不需要维度的数组。这使您可以解决许多技术计算问题，尤其是那些具有矩阵和向量公式的问题，而只需用 C 或 Fortran 等标量非交互式语言编写程序所需的时间的一小部分。MATLAB 名称代表矩阵实验室。MATLAB 最初的编写目的是提供对由 LINPACK 和 EISPACK 项目开发的矩阵软件的轻松访问，这两个项目共同代表了矩阵计算软件的最新技术。MATLAB 经过多年的发展，得到了许多用户的投入。在大学环境中，它是数学、工程和科学入门和高级课程的标准教学工具。在工业领域，MATLAB 是高效研究、开发和分析的首选工具。MATLAB 具有一系列称为工具箱的特定于应用程序的解决方案。对于大多数 MATLAB 用户来说非常重要，工具箱允许您学习应用专业技术。工具箱是 MATLAB 函数（M 文件）的综合集合，可扩展 MATLAB 环境以解决特定类别的问题。可用工具箱的领域包括信号处理、控制系统、神经网络、模糊逻辑、小波、仿真等。