I need to decide between three options: a) spend my holiday in London; b) spend my holiday in Norwich; c) stay at home. My decision depends on two independent variables: 1. the chances that it will rain (expressed in percentages), 2. the strength of my preferences for each of three places (expressed in numbers).

As for the first variable, there is a 30% chance that it will rain in London, 5% that it will rain in Norwich and 10% for raining in my city. As for the second variable, my preference for going to London has the value of 9, for Norwich 6.7 and for staying at home 6.

What would be the formula for calculating the values from the two variables? Would simply the multiplication of the percentages with the whole numbers be a valid operation here?

Thanks for your help.

Alex