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The following table gives the frequency distribution of the weights (in pounds).
Weight (in pounds) f midpoints f*mid cummulative f
90 – 109 8
110 – 129 17
130 – 149 21
150 – 169 24
170 – 189 19
190 – 209 11
sums
a. Fill out the table above.
b. Do all classes have the same width? If yes, what is that width?
c. Use the table to estimate the average weight.
d. Draw an ogive (line graph for the cumulative frequencies).
I have a question on how to find the average weight.Did we ever take notes on it ?
To estimate the weight:
1. multiply each midpoint by the respective frequency.
2. sum these products.
3. divide by n= sum of the frequencies
Perhaps we did not go over an example in class, but you are responsible as well for what appears in the text. On page 70, example 8 shows what should be done to find the mean for this situation.
weight (in lbs) frequency midpoint freq *mid cumulative freq
90-109 8 99.5 796 8
110-129 17 119.5 2031.5 25
130-149 21 139.5 2929.5 46
150-169 24 159.5 3828 70
170-189 19 179.5 3410.5 89
190-209 11 199.5 2194.5 100
Sums: 100 15190
b) yes, all classes have a width of 20 lbs
c)average weight is 151.9 lbs (15190 /100 =151.9)
d) i have the ogive on paper but don’t know how to do it on the computer.
I am sorry that the “table” came out so unclear i tried to put spaces in between the numbers so they should line up, but it didn’t post that way.
Thanks cmax for your effort. Yes, there is definite limitations to this tool. Perhaps using blackboard for discussion would have been better. As for the diagram, you can scan or take a picture of it and attach as a file.
Why is the width 20 lbs? When i did was 19 lbs? is it wrong?
The best way to find out the class width is to figure out how much it takes to go from the left endpoint of the first interval (90) to the left endpoint of the 2nd interval (110). Attached is the graph for the ojive. Don’t forget to create an extra row with the previous midtpoint and a 0% relative frequency.
An Ogive should have for the horizontal scale the upper class boundaries and NOT the midpoints. Page 45 on our textbook.
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