A Sales Letter, Private Investigation is a type of investigation that focuses on selling a product or service to a target audience. This type of investigation involves researching and assessing the target market's needs and preferences, analyzing competitor offerings, and creating a compelling sales message that can be used in various marketing materials. It may also involve researching customer feedback about existing products and services to identify areas of improvement or opportunities to create new products or services. There are two types of Sales Letter, Private Investigations: Pre-purchase and Post-Purchase. Pre-purchase investigations involve researching the target market, analyzing competitors, and creating a sales message prior to a customer making a purchase. Post-purchase investigations focus on analyzing customer feedback, identifying areas of improvement or opportunities to create new products or services, and devising strategies to increase customer satisfaction and loyalty.