a company wanted to see which sales letters is the most effective in making sales. they took a random sample of their past sales and sorted them by which of their 6 different letters were used to make the sale.

one of the 6 sale letters produced 50% more sales than the next best performing sales letter.

what conclusion can be drawn from this study?

a) it can be said there is a casual relationship between the sales letters and sales

b)conclusions cannot be made b/c there was not a control group

c)conclusions cant be made b/c the lurking variable of the customers income is confounded with the sales

d)there is clear evidence of an association between the sale letters and the ssales but it cant be said there is a casual relationship between the letters and the sale