2.1 Frequency distribution Ogive

Example: page 44, problem maxmin

-range = 73 – 50 = 23 -c.w. = 23 ÷ 6 = 3.8 → 4 -we will start the setup of the class limits with the minimum data value (50), to which we will add the class width (c.w.) -these are the lower limits (where each class begins)

Class limits TallyfClass boundary Cumu- lative freq. 50 – 54 – 58 – 62 – 66 – 70 –

-Next we determine the first class’ upper limit (where it ends) by subtracting 1 from the second class’ lower limit -54 – 1= 53 -then we add again the class width (4) to the upper class’ limits -tally

Class limits TallyfClass boundary Cumula- tive freq. 50 – 53/1 54 – – 61////4 62 – 65//// 9 66 – 69//// //7 70 – 73///3

-To find the class boundary we will subtract a half a unit (usually.5) from the lower class limits and add a half a unit (usually.5) to the upper class limits

Class limits TallyfClass boundary Cumula- tive freq. 50 – 53/149.5 – – – – 61////457.5 – – 65//// – – 69//// //765.5 – – 73///369.5 – 73.5

-We obtain the cumulative frequency by adding to the class’ frequency the frequencies of the classes above

Class limits TallyfClass boundary Cumula- tive freq. 50 – 53/149.5 – – – = 1 58 – 61////457.5 – = 5 62 – 65//// – = – 69//// //765.5 – = – 73///369.5 – = 24

OGIVE -Is an open line -Always rises (at least it is horizontal) -On the x-axis: class boundary -On the y-axis: cumulative frequency -Important: label the axis, name your graph