Presentation on theme: "SECTION 2.2 BUILDING LINEAR FUNCTIONS FROM DATA BUILDING LINEAR FUNCTIONS FROM DATA."— Presentation transcript:
SECTION 2.2 BUILDING LINEAR FUNCTIONS FROM DATA BUILDING LINEAR FUNCTIONS FROM DATA
LINEAR CURVE FITTING STEP 1: Ask whether the variables are related to each other. STEP 1: Ask whether the variables are related to each other. STEP 2: Obtain data and verify a relation exists. Plot the points to obtain a scatter diagram. STEP 2: Obtain data and verify a relation exists. Plot the points to obtain a scatter diagram. STEP 3: Find an equation which describes this relation. STEP 3: Find an equation which describes this relation.
FINDING AN EQUATION FOR LINEARLY RELATED DATA A farmer collected the following data, which shows crop yields for various amounts of fertilizer used. A farmer collected the following data, which shows crop yields for various amounts of fertilizer used.
GETTING A SCATTER PLOT OF THE DATA Ensure that all equations in the Y= menu are cleared out or disabled. Input the data into the lists in the statistics editor: STAT 1:Edit Turn on a Statistics Plotter and set the desired parameters: 2nd Y= Push Zoom and choose ZoomStat.
GETTING A LINE OF BEST FIT Verify by the scatter plot that the data has a linear relationship. Go to the home screen, press STAT, arrow to CALC, and choose LinReg. A linear regression equation will appear in the home screen.
GRAPHING THE REGRESSION EQUATION To put the regression equation in the Y= menu: 1. Push Y= 2. Push VARS, choose Statistics, arrow to EQ, and choose RegEQ. Now push GRAPH.
MAKING A PREDICTION Use the Linear Regression Equation to Estimate the Yield if the farmer uses 17 pounds of fertilizer. 1. Go to home screen 2. Go into YVARS, choose Function, Choose Y 1. 3.Type in (17).
MAKING A PREDICTION Our prediction is that the crop yield for 17 Pounds of fertilizer per 100 ft 2 will be 17 Bushels
CONCLUSION OF SECTION 2.2 CONCLUSION OF SECTION 2.2
VARIATION Relationships between variables are often described in terms of proportionality. For Example: Force is proportional to acceleration. Pressure and volume of an ideal gas are inversely proportional.
DIRECT VARIATION Let x and y denote two quantities. Then y varies directly with x, or y is directly proportional to x, if there is a nonzero number k such that y = kx constant of proportionality
EXAMPLE For a certain gas enclosed in a container of fixed volume, the pressure P (in newtons per square meter) varies directly with temperature T (in kelvins). If the pressure is found to be 20 newtons/m 2 at a temperature of 60 K, find a formula that relates pressure P to temperature T. Then find the pressure P when T = 120 K.
SOLUTION First, we know that P varies directly with T. P = k T And, we know P = 20 when T = 60. Thus, 20 = k(60)
SOLUTION The formula, then, is Now, we must find P when T = 120K P = 40 newtons per square meter