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Wilcoxon Rank sum - urgent watch

1. Hi
i have a stats exam tomorrow, and looking through my notes, i do not understand Wilcoxon rank sum at all. To me it makes no sense, and looking online has confused me even further. Would anyone be able to explain it to me? Possibly with an example?

Thank you so much in advance
xx
2. (Original post by katechar_X)
Hi
i have a stats exam tomorrow, and looking through my notes, i do not understand Wilcoxon rank sum at all. To me it makes no sense, and looking online has confused me even further. Would anyone be able to explain it to me? Possibly with an example?

Thank you so much in advance
xx

to carry out a wilcoxin signed rank test ona SINGLE sample
:: stat H0 and H1
:: find the signed differences between each data value and the median
:: rank these differences starting from the smallest to the largest, in two lists + and -
:: calculate the totals for T+ and T- and let T be the smaller of these
:: compare to the critical value found in table ten (of blue AQA formula book)
:: reject HO if t < or = CV, otherwise accept H0
:: make a conclusion related to the original question

to carry out a paire wilcoxin rank test :
:: state H0 opulation mean differnece =0
H1: population median difference >, < or not equal 0
:: find the signed difference between each pair of data values
:: proceed as for a wilcoxin signed-rank test above

Good Luck with SS03 I hope this helps
3. i still dont understand it. I dont understand how i apply it to numbers. If i give you the question, would there be any chnace you could help? You would be an absolute star if you would.

A psychologist wanted to know whether the liking of a food was influenced by whether it was paired with images of obese or anorexic body shapes. The following preference ratings were given by people who had the food paired with either obese or anorexic images. Is there a significant difference?

Obese paired: 3, 5, 1, 4, 2, 2, 1, 10
Anorexic Paired: 5, 6, 7, 7, 8, 6, 9, 8, 6
4. (Original post by katechar_X)
i still dont understand it. I dont understand how i apply it to numbers. If i give you the question, would there be any chnace you could help? You would be an absolute star if you would.

A psychologist wanted to know whether the liking of a food was influenced by whether it was paired with images of obese or anorexic body shapes. The following preference ratings were given by people who had the food paired with either obese or anorexic images. Is there a significant difference?

Obese paired: 3, 5, 1, 4, 2, 2, 1, 10
Anorexic Paired: 5, 6, 7, 7, 8, 6, 9, 8, 6
H0: population median difference =0
H1: Population differnce does not = 0
two-tailed test

3-5 = -2
5-6= -1
1- 7= -6
4-7 = -3
2-8 = -6
2- 6= -2
1- 9 =-9
10 -8 = 2

T+ = 2 T-= 29 CV= (at 5% level) = 4

as 2 < 4 ( TS <CV) Reject H0 and conclude that there is a signicant evideence to show that preference ratings were given by people who had the food paired with either obese or anorexic images
5. What happens to the 6 that hasnt been matched? Thank you so mucg btw

(Original post by oxPENELOPExo)
H0: population median difference =0
H1: Population differnce does not = 0
two-tailed test

3-5 = -2
5-6= -1
1- 7= -6
4-7 = -3
2-8 = -6
2- 6= -2
1- 9 =-9
10 -8 = 2

T+ = 2 T-= 29 CV= (at 5% level) = 4

as 2 < 4 ( TS <CV) Reject H0 and conclude that there is a signicant evideence to show that preference ratings were given by people who had the food paired with either obese or anorexic images

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