Ngene 1.2 离散选择实验设计生成软件at卡贝

Ngene软件

Ngene是用于生成实验设计的软件，其用在所述选择实验(stated choice experiments)中以估计选择模型，特别是logit类型。 它被全世界50多个国家的研究人员，顾问和学生使用。

Ngene具有现代化的图形界面和最先进的方法，可用于生成各种实验设计。 Ngene允许生成正交设计，最佳正交设计和有效陈述选择设计。 Ngene 1仅支持正交主效应设计和高效设计，支持MNL，MMNL面板和横截面以及EC面板和横截面模型的主效应和交互效应。 Ngene还允许对不同类型的设计进行约束和属性嵌套。 Ngene允许用户打开和读取现有数据，例如评估可能在其他地方生成的设计。

允许用户为任意设计构建HTML代码 用户可以采用现有设计（甚至是使用其他软件生成的设计）并逐步构建用于呈现该设计的HTML代码。 用户必须编写自己的代码以使用设计捕获数据，但是对于那些希望向客户展示实验在实践中可能看起来像什么的人来说，此功能将允许快速解决，而无需首先自己编写完整的调查。

Stated choice surveys and experiments consist of a series of hypothetical choice tasks that are used to elicit and preferences consumers, patients, farmers, , and other agents in order to determine willingness to pay for market and non-market goods, and predict market shares and demand elasticities of future products.

Created by leading experts in the area of discrete choice modelling, includes state-of-the-art methods to generate the best choice tasks in a survey in order to information and sample size, while at the same time ensuring that choice tasks are familiar, realistic, and not too complex.

特征

is capable of generating design types for a wide range of discrete choice experiments and model types. assists you in getting the most out of a survey by information and making choice tasks more realistic and familiar to respondents.

灵活性

is syntax based in order to allow maximum flexibility in specifying the dimensions of your design. You can generate designs with any number of labelled and/or unlabelled alternatives (including a status quo alternative or a ‘no choice’ alternative), any number of choice tasks, any number of attributes, and any number of attribute levels. Further, in Ngene you can control design properties such as attribute level balance, orthogonality, correlation structure, minimum overlap, and blocking.

容易使用

All outputs in Ngene can be easily copied and pasted into other software such as Excel for further analysis and use. Further, Ngene can read in externally generated designs or data and evaluate efficiency, correlations, choice probabilities, etc. Syntax files, data files, and design outputs can be saved in a project. Multiple algorithms exist for generating designs that run without the need to change the default settings, although more advanced users may wish to take advantage of additional control. Further, inspecting an experimental design matrix is made easy in Ngene by being able to show quick mockups of formatted choice tasks. Ngene includes an extensive manual that details how to use Ngene, and introduces stated choice experimental design theory.

INFORMATION MAXIMISATION

In order to select the best design, Ngene allows the user to fully specify the model(s) that would most likely be estimated. This includes selecting the model type and formulating the utility functions with main effects and interaction effects, linear and nonlinear effects (using dummy or effects coding). Current supported model types are the multinomial logit model as well as (cross-sectional and panel) mixed logit and error component models. A range of efficiency criteria is available in order to maximise information when estimating the model parameters or willingness-to-pay, including D-error and A-error. Prior information about the parameters can be provided in order to further optimise the design. Ngene supports fixed priors as well as uniformly and normally distributed priors (i.e. Bayesian efficient designs) to account for uncertainty in the prior values. When priors are provided, Ngene automatically calculates the expected sample size required for estimating the model parameters at a given level of statistical significance. In order to minimise computation time for Bayesian and mixed logit designs, Ngene can take smart draws from random distributions, including quasi-random draws (such as Halton draws, Sobol draws, MLHS) and Gaussian quadrature. Ngene also supports optimising over multiple model specifications and efficiency measures at the same time.

ADVANCED CONSTRAINTS

Ngene gives the user complete control with respect to the combinations of attribute levels that are considered feasible in order to enhance realism in the design. This is done by including conditional constraints (if…then), through setting requirements on attribute level combinations that cannot occur or that should occur, or by introducing scenario variables. For very complex and heavily constrained designs, the user also has the option to externally create candidate sets with feasible choice tasks (e.g. in Excel) and read them into Ngene. This method can also be used for other advanced designs in which the user wishes to limit the number of alternatives or attributes shown to a respondent in each choice task in order to reduce choice task complexity.

NO SILLY CHOICES

It is important that problematic choice tasks, such as choice tasks in which there are no trade-offs or where one of the alternatives is strictly dominant, are not present in the experimental design in order to avoid possible parameter biases in model estimation. While this is often considered a manual job, Ngene can automatically detect such problematic choice tasks and avoids including them in the experimental designs.

TAILORED DESIGNS

Instead of using a fixed set of choice tasks shown to respondents, Ngene can create designs in which the attribute levels are pivoted around the reference levels of the individual respondents. This makes the choice context more familiar and reduces hypothetical bias. To achieve this, Ngene allows the inclusion of a reference alternative while the levels of the other alternatives are absolute or relative differences to the reference levels. Furthermore, it is also possible to create different designs for different segments within the population by including one or more socio-demographic variables in the utility functions.