Question

a)    A Department of Environment technician was conducting a study on the concentration level of lead (Pb) in ex mining Sri Murni pond in Gombak, Selangor. Ten samples were collected, and the data obtained are given below;

Sample No.	Pb level (ppm)	Sample No.	Pb level (ppm)
1	4.6	6	6.3
2	3.7	7	4.8
3	5.1	8	5.5
4	4.2	9	10.1
5	7.8	10	7.2

i.          The Pb level in sample number 9 appeared to be off compared to the other 9 samples. Show an appropriate calculation to suggest if the data should be retained or rejected.

ii.          Calculate the average Pb level contained in the pond, taking into consideration the acceptance or rejection of sample number 9. Write the mean in three significant numbers.

iii.          Use an appropriate statistical test to ascertain whether the calculated average Pb level is significantly different compared to the certified value of 6.5 ppm as determined by the relevant standards laboratory just the week before.

Answer 1

t table as follows: