Calculation of "Sampling Weight"

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Nilu Babu

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Jul 27, 2022, 4:26:41 AMJul 27
to Biogeme
Dear Concern
Dear Prof. Bierlaire,

I hope this email finds you well.

I have recently started course on Discrete Choice Modelling and facing some difficulties on survey data. For simulation  "Switzerland mode choice" data named "Optima" is used. In that survey data there is a column named "Weight" and I am not understanding how to calculate this data for every individual especially when the variable is more than one.  I have attached the data file in excel format which is already in the website for your kind reference.

I would be grateful to you if someone could explain this calculation.

Regards
Nilu 
optima.xlsx

Bierlaire Michel

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Jul 27, 2022, 4:30:33 AMJul 27
to niliub...@gmail.com, Bierlaire Michel, Biogeme
THe population is segmented based on 6 socio-economic characteristics, as described in the document. 

The weight is the ratio between the share of persons in the corresponding segment in the population, and the share of persons in the corresponding segment in the sample. 

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<optima.xlsx>

Nilu Babu

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Jul 27, 2022, 11:47:03 AMJul 27
to Bierlaire Michel, Biogeme
Thank you professor for your kind response. I got the point that "The weight is the ratio between the share of persons in the corresponding segment in the population, and the share of persons in the corresponding segment in the sample". But I couldn't understand why the summation of the "Weight" is 1 (in the Optima file) . Is it the probability of an individual?

Bierlaire Michel

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Jul 27, 2022, 11:47:46 AMJul 27
to niliub...@gmail.com, Bierlaire Michel, Biogeme

On 27 Jul 2022, at 11:22, niliub...@gmail.com wrote:

Thank you professor for your kind response. I got the point that "The weight is the ratio between the share of persons in the corresponding segment in the population, and the share of persons in the corresponding segment in the sample". But I couldn't understand why the summation of the "Weight" is 1 (in the Optima file) . Is it the probability of an individual?

It is just a normalization.

Nilu Babu

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Jul 28, 2022, 2:39:33 AMJul 28
to Bierlaire Michel, Biogeme
Thank you for the clarification. 
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