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Standard deviations help :-(

Sparrow_Hawk · 2014-04-30 15:20:45

Cant get my head around standard deviations, hoping someone can help. I get the bit where the average score is 35.54 and most subjects scored +- 0.74 of 35.54. The total marking for the assessment is 36. My subject got 33/36 and 27/36 how good or bad is this?? Does it mean if my subject got (for the first one) 33 and the…

30-04-2014 3:20pm

#1

Sparrow_Hawk

Registered Users, Registered Users 2 Posts: 50 ✭✭

Join Date: June 2011

Posts: 31

Cant get my head around standard deviations, hoping someone can help. I get the bit where the average score is 35.54 and most subjects scored +- 0.74 of 35.54.
The total marking for the assessment is 36. My subject got 33/36 and 27/36 how good or bad is this?? Does it mean if my subject got (for the first one) 33 and the mean is 35.54 – and because 35.54 minus SD (0.74) is still higher than 33, my subject is 3 SD below the average population (controls)? Does this mean they are in the bottom 0.1 of the population?
Lets say they got 10/36, would the ceiling effect mean this score would not have any significance i.e. the participants “broke” the test!

24 control subjects
Mean 35.54
SD 0.74
Also
Mean 34.83
SD 2.58

Second assessment - 25 control subjects
Mean 39.00
SD 1.70

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