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Published byTyrone Hill Modified over 9 years ago
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2.1 Frequency distribution Histogram, Frequency Polygon
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Example: page 43, problem 17 21142468100018764278 10302000107739811643 18581500410531831932 13555835151216972478 46087119 max min
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-range = 7119 – 1000 = 6119 -c.w. = 6119 ÷ 6 = 1019.8 → 1020 -we will start the setup of the class limits with the minimum data value (1000), to which we will add the class width (c.w.) -this are the lower limits (where each class begins)
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Class limitsTallyfClass midpoint 1000 – 2020 – 3040 – 4060 – 5080 – 6100 -
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-Next we determine the first class’ upper limit (where it ends) by subtracting 1 from the second class’ lower limit -2020 – 1= 2019 -then we add again the class width (1020) to the upper class’ limits
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Class limitsTallyfClass midpoint 1000 – 2019 2020 – 3039 3040 – 4059 4060 – 5079 5080 – 6099 6100 – 7119
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-now we evaluate the first classes midpoint by adding the two class limits and divide by 2 -1000 + 2019 = 3019 -3019 ÷ 2 = 1509.5 -Then we add the class width to the midpoint
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Class limitsTallyfClass midpoint 1000 – 20191509.5 2020 – 30392529.5 3040 – 40593549.5 4060 – 50794569.5 5080 – 60995589.5 6100 - 71196609.5
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-Now we tally
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Class limitsTallyfClass midpoint 1000 – 2019//// //// //121509.5 2020 – 3039///32529.5 3040 – 4059//23549.5 4060 – 5079///34569.5 5080 – 6099/15589.5 6100 - 7119/16609.5
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HISTOGRAM -Is a bar graph with vertical bars -The bars are equal in width -The bars do touch each other -On the x-axis: class midpoint -On the y-axis: frequency -Important: label the axis, name your graph
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FREQUENCY POLYGON -Is a closed shape -On the x-axis: class midpoint -On the y-axis: frequency -Important: label the axis, name your graph -Me might have to extend the marks on the x-axis to the left and/or to the right with one more class width.
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