Why do methods of selection differ from variable to variable?
The method of selection depends on the type of variable. If it is numerical, like “Voyage identification number” or “Year arrived with slaves” or “Total slaves embarked,” one is asked to enter a specific number or range of numbers. If it is a name, like that of a ship or its captain or the owner of the venture, one is asked to enter the name or part of it. If the variable consists of a set of categories, such as places or types of outcome of a slaving voyage, then the categories are listed with small check boxes in front of them and one is asked to check those that correspond to categories about which to find information. If there is an arrowhead in front of the checkbox, click on it to reveal further options.
