# Urgent. i have test tmr.Statistics

• Mar 31st 2009, 01:17 AM
helloying
Urgent. i have test tmr.Statistics
the qn is in a table format.
Marks 10 20 30
no. of pupils 16 10 x

(a)if the median mark is 20, find the range of x. i am not sure how to do but my ans is 9 to 16. i think i am wrong

(b)find x if the mean mark is 16. i got x=4
• Mar 31st 2009, 04:45 AM
mr fantastic
Quote:

Originally Posted by helloying
the qn is in a table format.
Marks 10 20 30
no. of pupils 16 10 x

(a)if the median mark is 20, find the range of x. i am not sure how to do but my ans is 9 to 16. i think i am wrong Mr F says: If x = 9 the middle value is the 18th (which is 20). If x = 8 the middle values are the 17th and 18th (which is still 20). If x = 16 the middle values are the 21st and 22nd (which is 20). If x = 25 the middle value is the 26th (which is still 20). Therefore the range for x is ......

(b)find x if the mean mark is 16. i got x=4

(b) [(16)(10) + (10)(20) + x (30)]/(16 + 10 + x) = 16 => (360 + 30x)/(26 + x) = 16 => x = 4. (Clapping)
• Apr 1st 2009, 03:31 AM
helloying
Quote:

Originally Posted by mr fantastic
(b) [(16)(10) + (10)(20) + x (30)]/(16 + 10 + x) = 16 => (360 + 30x)/(26 + x) = 16 => x = 16. (Clapping)

i think u typed wrongly. Isnt x=4 ? :)
• Apr 1st 2009, 03:40 AM
mr fantastic
Quote:

Originally Posted by helloying
i think u typed wrongly. Isnt x=4 ? :)