When a question requires a decimal number as a response, define it in the Metadata section of the interview script as:

You specify valid responses for decimal questions in the same way as for integer questions, so single values, fixed and open-ended ranges, lists of single values and ranges, and exclusive values are all acceptable. For more information, see Questions with integer responses.

Decimal responses are stored in the case data as double variables; that is, as 64-bit floating point values with 15 digits of precision. You can control the data format by specifying:

Decimal responses are stored in the case data as double variables; that is, as 64-bit floating point values with 15 digits of precision. You can control the data format by specifying:

The character you use for the decimal point when specifying values depends on your computer’s locale/culture/language setting. For example, if your setting is en–UK, use a dot (1.2, for example); if your setting is en–DA, use a comma (1,2). The character that respondents must use depends on the language that the script sets for the interview or, if none is set, the language set for the respondent’s browser.

You can make the decimal point character independent of the interview language by specifying a language in the IOM.Locale property. The Locale property defines the language to use for data input and output and response validation. Normally, it is the same as the IOM.Language property, so if the language changes so does the locale. If you want all respondents to use the same character for the decimal point, you might specify a language that uses that character as the interview locale. For example, if you want all respondents to use a dot for the decimal point, set IOM.Locale to English (for example, en–us). This overrides the language setting, so respondents might see questions and responses in French, but they still have to enter prices and similar values in the English format. See also “Allowing a thousands separator character.

Specifying the locale manually breaks the link between the two properties so any subsequent language changes do not affect the locale setting.

To specify the maximum number of digits that can be written, append the precision keyword to the standard question definition:

where <number_of_digits> is the maximum number of digits.

In the following example, the weight will always be written as four digits.

To specify the maximum number of decimal places that can be entered, append the scale keyword to the standard specification:

where <number_of_digits> is the maximum number of decimal places.

In the following example, more than two decimal places cannot be entered for the price of the meal:

The interviewing program does not normally accept a thousands separator character in large numbers. For example, in countries that use the comma as the thousands separator, the number 1,512.89 will be rejected even if it is within the range specified for the question. If you want the interviewing program to accept thousands separators in numeric responses, place the following statement in the routing section of the questionnaire before the question is asked:

where <question_name> is the name of a question with a numeric response.

The character that the interviewing program accepts as the thousands separator depends on the language or locale set for the interview. The language can be set in the script itself, otherwise it defaults to the language set in the respondent’s browser. This can be overridden by setting the interview’s locale in the script. The Locale property defines the language to be used for data input and output and for validation. For example, if the interview language is set to French, the interviewing program expects respondents to use a space as the thousands separator and a comma as the decimal point. If the script sets the locale to English, the interviewing program will then expect a comma for the thousands separator and a dot for the decimal point.

The Locale property normally mirrors the Language property so that when the language changes so does the locale. However, if you specify the locale manually this breaks the link between the two properties and any subsequent language changes do not affect the locale setting. For more information, see Using locale to control decimal number and date formats.

AllowThousandsSeparator is provided primarily to maintain backwards compatibility with early versions of the interview scripting language, in which the default was to require the use of thousands separator characters.

Comparing two double values that look the same with the “equals” operator can return unexpected results, because of differing precision.

This script shows some ways of comparing double values: