madhu.mukherjee.946 one year ago calculate the arithmetic mean: age group: 14-15 16-17 18-20 21-24 25-29 30-34 35-39 no.of wage earners: 60 140 150 110 110 100 90

its difficult to calculate the mid value here coz the common difference is changing

2. Nnesha

hmm don't we hve to add all the numbers and divide by the number of numbers

3. Nnesha

tag ganeshie8 or freckles

4. Nnesha

@ganeshie8 @freckles

6. freckles

@Nnesha is right

7. freckles

just add the numbers and divide by the number of numbers

no in group frequency we don't solve it like that way

9. freckles

oh I see the mid value is just the sum of endpoints and that result divided by 2

10. freckles

for example: $\frac{14+15}{2}=\frac{29}{2}=14.5$

11. freckles

so x_1=14.5 and f_1=60 x_1*f_1=14.5*60

12. freckles

$\text{ mean }=\frac{x_1 f_1 +x_2 f_2 +x_3 f_3+x_4f_4+x_5f_5+x_6f_6+x_7f_7}{f_1+f_2+f_3+f_4+f_5+f_6+f_7} \\$

13. freckles

at least that is my definition of midpoint http://www.yale.edu/ynhti/curriculum/units/1986/5/86.05.03.x.html here they pick the midpoint of 99 to 100 as 98 which is odd because that is not the midpoint of 99 to 100

14. freckles

thank you so much

16. freckles

@madhu.mukherjee.946 still trying to figure out how to pick h |dw:1440874552930:dw| so I think I will choose a to be that thingy there because it looks like they are picking a to be one of the "middle numbers" and we only have one middle here since we have an odd amount of data entries do you ever seen this method? And do you know how to pick h?

17. freckles

|dw:1440874856438:dw|

18. freckles

the next column involves the h value and I'm still trying to find out how they picked in the last example or two

19. freckles

I guess we can just see what happens if we pick h to be 2

20. freckles

|dw:1440875337918:dw|