VISUALIZING DATA Ch. 2 Sect. 3

Graphing Data Charts are used to help analyze data Independent variable  Variable that is changed or manipulated  Experimenter can control directly Dependant variable  Outcome of dependant “depends” on the independent variable

Graphing Circular objects Use a meterstick to measure the diameter of four circular objects and a string to measure circumference ObjectDiameterCircumference

Graphing Data Use the data and make a circumference vs. diameter graph  X-axis = Diameter  Y-axis = circumference The graph shows a linear relationship  Slope should be about 3.14  Expressed as circumference = 3.14 x diameter  Formula  Equals Pi (л)

Linear Relationships Straight line through all data points  Dependant varies linearly with Independent  Y = mx + b Slope (m) is the ratio of vertical change to the horizontal change  Find by selecting 2 points far apart  Should not be data points but points on the line  m = Δy (rise) / Δx (run)

Linear Relationships Y – Intercept (b) is the point at which the line crosses the y-axis when the value of x is zero  When y-intercept is zero, b = 0, equation is y = mx

Non-linear Relationships When graphs being presented are not in a straight line Graphed in a curved line or Parabola  Related by the Quadratic Relationship  y = ax 2 + bx + c  One variable depends on the square on another

Non-linear Relationships

Inverse repationships  Hyperbola  One variable is dependant on the inverse of another  y = (a / x) or xy = a  a is constant