• 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

## 商科代写|商业建模代写Business Modeling代考|Using Audit Tools to Find and Correct Errors

When inheriting a model, there are several factors to come to grips with: the layout, design, formatting, assumptions, and formulas. Of all these, following the formula calculations is the most difficult, and verifying and validating formulas can be very time-consuming. The fastest way to understand a formula when you see it for the first time is to go into Edit mode. Double-click a cell, or select it and press F2. If the formula’s source inputs are on the same page, they’ll show visually where the source data is coming from that feeds the cell calculation, as shown in Figure 5-5. The color codes are helpful; each range in the formula will be the same color as the highlight source data that feeds it. If you’d like to try this out for yourself, download File $0501 . x l s x$ from www. dummies.com/go/financial model inginexcel fd2e. Open it and select the tab labeled $5-5$.When you’re in Edit mode and you decide that you need to change the range the formula is referring to, you can use the mouse to click and drag the colored lines to reference a different cell. For example, in Figure $5-5$ if you want the range B3:B12 to be A3:A12 instead, click the colored line showing between the A and B column and drag it so that the cell reference is column A instead of column B.

On the Formulas tab in the Ribbon, there is a formula auditing section that contains a number of tools that you’ll find useful when trying to understand someone else’s financial model. Just remember that using these audit tools in Excel is not the same as performing a formal financial model audit.

A formal financial model audit is a very detailed process in which a model auditing team takes the model apart and checks it meticulously for errors. If the bank is lending you money based on the results of the financial model, one of the conditions of the loan might be that the model be audited to make sure that the results can be relied upon. Getting a model professionally audited can be an extremely expensive undertaking, but it’s really the only way to ensure that there are no errors. Note that a financial model audit is sometimes called a model review to differentiate it from a financial audit.

Of course, creating your own financial model is a lot more interesting than checking someone else’s. But Excel’s audit tools make checking someone else’s model somewhat easier. Formula errors are the most common type of error in financial models, and the audit tools exist almost solely for the purpose of finding these formula errors.

## 商科代写|商业建模代写Business Modeling代考|Checking a model for accuracy

The formula auditing tools can help get to the root of what’s causing the error in a cell through tracing relationships among cells within your worksheet. These tools will help you find the source of an error, but they’ll also, more importantly, help you find an error you didn’t know was there. By tracing the relationships, formula auditing lets you test formulas to see the precedents (cells that directly supply the formulas) and the dependents (the cells that depend on the results of the formulas). Excel also offers a way to visually reverse any potential sources of an error in the formula of any particular cell.

The formula auditing tools can be found in the command buttons located in the Formula Auditing group on the Formulas tab of the Ribbon. These command buttons include the following:

) Trace Precedents/Trace Dependents: In trying to understand a model, you’ll spend the majority of your time working through the formulas and making sure you understand exactly how each output has been calculated. Trace Precedents and Trace Dependents are good places to start when you’re trying to see where the cell links are coming from and going to. These tools are helpful to identify the linkages that exist between the cells and display the relationships visually with blue tracer line arrows.To use Trace Precedents, start with an output cell that contains a formula you want to understand, such as the formula in cell G26 in Figure 5-6. Select the cell and click the Trace Precedents button in the Formula Auditing section of the Formulas tab. This displays blue tracer line arrows, which show which cells G26 depends on.

Mixed cell referencing is a combination of relative and absolute referencing; one part of the reference is absolute, and the other is relative. When you add a dollar sign before the row, the row remains anchored when the cell is copied; when you add a dollar sign before the column, the column remains anchored when the cell is copied.

For example, if you create the reference =B2 in a cell, and then copy that reference down, it will change to $B 3$. If you add some anchoring, here are the results in each case:
\begin{tabular}{l|l}
Cell & Copies as Cell \
\hline$=\mathrm{B} 2$ & $=\mathrm{B} 3$ \
\hline$=\$ \mathrm{~B} \$2$ & $=\$ \mathrm{~B} \$2$ \
\hline$=\mathrm{B} \$ 2$&$=\mathrm{B} \$2$ \
\hline$=\$ \mathrm{~B} 2$&$=\$\mathrm{~B} 3$
\end{tabular}
The dollar sign anchors a row number or column letter when you copy it. You can anchor both the column and the row (absolute referencing), or you can anchor one or the other (mixed referencing).

Mixed cell referencing is a concept critical to good financial modeling practice, so it’s important for a financial modeler to understand this fundamental concept. Used effectively, mixed cell references make your model

Faster to build and more efficient
3) Less prone to error
3) Quicker, easier, and cheaper to audit
The easiest way to quickly add absolute and mixed cell referencing is to press F4 immediately after adding the reference to the formula. This keyboard shortcut cycles through combinations of relative and absolute referencing. You can repeatedly press F4 after entering the cell name in a formula to cycle through the mixed references. For example, type $=\mathrm{B} 2$ and then press $\mathrm{F} 4$ to display $=\$ \mathrm{~B} \$2$. Press $\mathrm{F} 4$ again to display $=8 \$ 2$. Press$\mathrm{F} 4$again to display$=\$82$. And press $\mathrm{F} 4$ again to display $=B 2 .$

Let’s look at a practical example of how to use mixed cell referencing. In the following example, you want to calculate how much you’d receive in interest under three different portfolio amounts and three different interest rates. The most efficient way to perform this calculation is to create a single formula with appropriate references and then copy that formula to other cells. You need to create a formula that multiplies the interest amount in row 1 and the borrowing amount in column A.

Instead of creating nine different formulas, you’re creating only one single formula using mixed cell referencing, which you can then copy across, saving you time and reducing the possibility of error.

## 商科代写|商业建模代写Business Modeling代考|Checking a model for accuracy

) Trace Precedents/Trace Dependents：在尝试理解模型时，您将花费大部分时间研究公式并确保您准确了解每个输出是如何计算的。当您尝试查看单元格链接的来源和去向时，跟踪先例和跟踪依赖项是很好的起点。这些工具有助于识别单元格之间存在的联系，并使用蓝色跟踪线箭头直观地显示关系。要使用跟踪先例，请从包含您想要理解的公式的输出单元格开始，例如单元格 G26 中的公式在图 5-6 中。选择单元格并单击“公式”选项卡的“公式审核”部分中的“跟踪先例”按钮。这将显示蓝色示踪线箭头，显示 G26 所依赖的单元格。

\begin{tabular}{l|l} 单元格并复制为单元格 \\hline$=\mathrm{B}2$ & $=\mathrm{B}3$\\hline$=\$\mathrm{~B} \$2$&$=\$\mathrm{~B}\$2$\\mathrm{B}\$2$&$=\mathrm{B}\$2$\\hline$= \$\mathrm{~B} 2$ & $=\$\mathrm{~B}3$\end{表格}\begin{tabular}{l|l} 单元格并复制为单元格 \\hline$=\mathrm{B}2$&$=\mathrm{B}3$\\hline$=\$\mathrm{~B} \$2$&$=\$\mathrm{~B}\$2$\\mathrm{B}\$2$&$=\mathrm{B}\$2$\\hline$= \$\mathrm{~B} 2$&$=\$\mathrm{~B}3$\end{表格}

3) 更不容易出错
3) 审核更快、更容易、更便宜

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## MATLAB代写

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