The Global Positioning System (GPS) may be one of the largest technological advances of the human beings. This technology became an essential component of most vehicles including airplanes, cars and ships. This device can be used anywhere around the world. While GPS was made for outdoors, there are major problems about indoor localisation. There are some useful indoor localisation tools that have been researched, such as WiFi and ZigBee technology. But due to the inaccuracy as well as interference that can occur in indoor locations, such as walls, other Wireless Sensor Networks (WSNs) and human interference, the recent systems that have been created, are still deemed to be unstable. Thus the increase of precision is required for these indoor systems. This research investigated the relationships between signal strengths and distance in the real situation. The data set obtained was analysed by using a regression method. Sensitivity was studied with Confidence Interval. The outcome of this research is expected to provide the users with a practical guideline for signal strength based localisation.