are you able to use this test if your two samples (A and B) each have a different n number? for example, i have 18 data points in my A group and 11 in my B group
go to the part where you average two data points' ranks (4+5)/2=4.5. Where else in the video do you use this information to calculate the U statistic? You do calculate the ranks, but you never use the information to calculate the U. Maybe I'm missing something because your example is too simplistic in that data sets A and B are strictly disjoint in that all a(i) is bigger (or smaller- I forget which) than b(i)
You are right about that second part, I could have used a better example for this. Points are given to each score from the B sample for all the A sample scores that are ranked above it, and vice-versa. The sum of points for both the B sample scores and the A sample scores are then found. The smaller of those two values becomes our "U". Let me know if it's still not clear.
The "U" statistic we calculate is used in calculating the z score. We calculate ranks because we're dealing with ordinal data - that is, data that has order, but no set difference between values. Look up "variable measurement scales" for an explanation that's a little bit better than that.
are you able to use this test if your two samples (A and B) each have a different n number? for example, i have 18 data points in my A group and 11 in my B group
crocodilerachel 2 months ago
Thanks for this review. Very helpful.'
God bless you Bother.
mysoukouss 7 months ago
You say it like DAY-ta americans! Say it right xD
jacksite2007 1 year ago
@jacksite2007
haha, I think I switch between both ways depending on which video you're watching. I can't make up my mind!
statslectures 1 year ago
What are the assumptions on the data that must hold for Mann-Whitney to be usable ?
angela1894 1 year ago
go to the part where you average two data points' ranks (4+5)/2=4.5. Where else in the video do you use this information to calculate the U statistic? You do calculate the ranks, but you never use the information to calculate the U. Maybe I'm missing something because your example is too simplistic in that data sets A and B are strictly disjoint in that all a(i) is bigger (or smaller- I forget which) than b(i)
merdirafiei 1 year ago
@merdirafiei
You are right about that second part, I could have used a better example for this. Points are given to each score from the B sample for all the A sample scores that are ranked above it, and vice-versa. The sum of points for both the B sample scores and the A sample scores are then found. The smaller of those two values becomes our "U". Let me know if it's still not clear.
statslectures 1 year ago
My original question stands: where in the video do you use the ranks to calculate the z statistic? Nowhere, right?
merdirafiei 1 year ago
@merdirafiei
The "U" statistic we calculate is used in calculating the z score. We can't find the U score without first finding the ranks.
statslectures 1 year ago
where is the Rank used in the final calculation of the Z-value? What's the point in calculating the ranks?
merdirafiei 1 year ago
@merdirafiei
The "U" statistic we calculate is used in calculating the z score. We calculate ranks because we're dealing with ordinal data - that is, data that has order, but no set difference between values. Look up "variable measurement scales" for an explanation that's a little bit better than that.
statslectures 1 year ago