14C: scatterplots

Line of best fit and Making predictions When you have a scatterplot, a line can be drawn which is as close as possible to all the data points (not joining all the dots!) This is called the line of best fit and is positioned by eye so that there is an equal number of points above and below the line Predictions can be made about values of data within the data set using this line Predictions made outside the data set are not considered reliable

Worked example Data was collected to investigate whether the outside temperature is related to the number of people preferring to spend time in a recreation room at an island resort. Propose a question that this set of data might be able to answer. Do more people go to the rec room when the temperature is higher or lower? Draw a scatterplot of the data. Temperature is the IV, so this is the X axis People in room is the DV, so this is the Y axis Label the axis, write intervals and plot the data Describe the trend shown by the scatterplot. Strong negative correlation (as temperature increases, the people in the rec room decreases)

Line of best fit and making predictions Consider the scatterplot from before. Draw the line of best fit. Use the line of best fit to predict: the temperature outside when 22 people are in the room Approx 29 degrees the number of people in the room when the outside temperature is 17 C Approx 44 people the number of people in the room when the outside temperature is 50 C. Zero Comment on your answers from part b. As the temperature increases, the number of people in the rec room dramatically decreases

Questions to do: 14 C page 488 questions 1, 2, 3, 4, 6, 9