Friendly Fit (FF) FF is a public limited company that owns a popular social media and fitness app. The app was launched five years ago and now has over three million users worldwide. The app allows users to upload and share pictures and short films of their favourite exercises. There are many other features which have been developed as the app has gained popularity. The app can be downloaded for free and users can access basic features without paying any money. However, to access all the features of the app, customers must pay a monthly fee of $10. FF also receives income from advertising revenue. Table 1.1 shows cost and revenue data for the app for the last two years. Table 1.1: FF's costs and revenue for the app for 2021 and 2020 2021 2020 ($m) ($m) Revenue from monthly fees 1.6 1.4 Revenue from advertising 1.4 1.8 Total costs 2.0 2.0 Every month, FF carries out a survey of a sample of users to research new features which may be added to the app. The sampling process is outlined in Fig. 1.1. A stratified sample based on age. Those who respond are given one month's free access to all the features of the app. Survey sent through the app to 50000 current users. 15000 users usually respond to the survey each month. [Figure 1.1]