00:01
Dear student, here is a question about the weight and number of children under that weight of usa in 2012.
00:14
So let's see what we have to do is first we have to find the standard deviation of these data.
00:26
For that first we have to complete this table as i have mentioned here.
00:31
To find xi what we have to do is xi mean that the lower boundary and the upper boundary difference mean 0 minus 9 9 and 9 then divide it with 2.
00:59
So when we divide this with 2 we get the xi.
01:04
The same will be 100 minus or we can say the upper boundary and the lower boundary.
01:13
First let's 1 9 0 0 minus 100 then we will divide it with 2.
01:23
So we will find the average.
01:25
So xi is actually the average of the class boundaries.
01:32
So what are the xi of these numbers? let's see it.
01:44
So the next thing in this question is table is to find the fi and xi.
02:12
Fi and xi mean fi will multiply with xi.
02:17
Here we can see that this number will multiply with 500.
02:22
So 27000 will multiply with 500 and we get the fi and xi value.
02:31
Same will be the second 90 000 plus sorry time 1500 and we will get the values and the values are here and we can see the other values down.
03:11
This is the sum of fi and xi.
03:14
It is important to find the mean of the data.
03:20
So we will highlight it with red.
03:24
Now the next in the table is to find the value of xi minus mean.
03:33
So here we can see that mean is not mentioned here.
03:38
So what we do to find the mean is we put the formula that is we'll do it down here that is mean equals to summation fi xi by summation fi.
04:04
So here we can see that summation fi xi is this one and summation fi is here.
04:18
So let's put the value that is one two nine five eight five zero zero zero zero zero by three nine four nine zero zero zero.
04:40
So we get the x value that is let's write here mean equals to three comma two eight one point four six.
04:56
So this is the mean and we will use it to complete this table above.
05:05
To find these value xi is here that is 500.
05:09
For example i will do it for the first question 500 then minus it with the mean.
05:15
Mean is as we find it now that is two three two eight one point four six as i have here.
05:30
We just have to minus it and we get the values and the values will be might be in minus and some are in positive.
05:41
So this one will be negative two seven eight one point four six like this.
05:48
So let's see the values here.
06:09
So the values are here given some are in negative and some are in positive because the mean if the mean and so xi value is greater than the mean then it will not be in negative.
06:27
At last we have to find the we have to just take square of this and then multiply it with fi.
06:35
So let's see how we will do this.
06:37
For example if it is minus if it is minus two seven eight one point four six we just take square of it then we multiply it with the f1 in this row that is twenty seven zero zero zero.
07:09
So we will get the values for each of the below...