You are getting into stats and I have to warn you that the condition of my stats knowledge is almost as limited as what I know about Biology which is practically nothing. But let's see if we can do something about this.
The first thing you have to do is make sure that the sales reps face the same conditions. Geography is going to matter. Start with the simple stuff. Does it matter whether or not the sales representatives were in the city of the country? If in the country, do the people have money enough to buy what is being sold? If in the city, what is the employment situation like? Make sure that you are comparing Apples and Apples.
What about crops? Do they matter? What about livestock does it matter? What do these rural areas need? Is he selling what they need? It's going to be harder to sell something in Detroit or Flint than it is San Francisco?
Did people experience a devastating winter? Especially in the Northeast? If they did, their heating bills are going through the roof. Literally. More money on heating less on whatever he's selling.
In short he has to consider conditions. Perhaps training will make no difference. There's other things that people have to live through. Maybe this was just a bad year. (It certainly was where I live. We got nothing but snow into mid April and East winds which are strong, cold, miserable and very nasty.)
Credit scores. I'd be well aware of any credit stats that I can obtain. What are people doing with their credit cards. You may be able to sell the stuff on credit, but will you ever receive payment that you can rely on or are these people one step away from bankruptcy? Is it different in the rural areas than in the cities? I can tell you I would hate to have it known that I disregard my credit cards in the town I live in (700 people). It would be cash only for everything.
Single or married? What's the demographics of the areas he's trying to sell in. We're retired. We don't take well to door to door sales people. Retired people have very little money to throw away on things we don't need. People on 3000 a month live very differently from those on 10000 a month.
Finally what's the competition like? Sears going under is a huge warning. Where do people get the products you are selling? This is especially important in rural areas. We have made over 170 mail purchases (we won't do that any more -- postage rates are just prohibitive).
If he has a sales force of 1000 people in 2 regions, he should think about moving some of them to other regions. Don't use this point.
Many of the things I've pointed out require a study before the the training is administered. You have to separate out what mitigates the efforts of the sales force and what they have little or no control over.
