Number 1 and 4 are wrong because the answers should be in 2s.f., number 2 you shouldn't use the anomalous result to calculate the mean, and then the answer is right.
Just try to find the mean values yourself. The first student is wrong because the mean will be 11 not 10.5. And the 4th student...I am unsure why it's wrong. 6 is an anomalous value and it should not be added in the mean but they havent added it. If i had this paper for the exam, I would answer B because 2 and 3 I am sure are correct. 1 is definitely wrong so not A or C. So I would go by the elimination method with these kind of questions.
Edit: 4th student is wrong because he/she didnt round off the number! Mean number of bubbles cannot be in decimals!
Just try to find the mean values yourself. The first student is wrong because the mean will be 11 not 10.5. And the 4th student...I am unsure why it's wrong. 6 is an anomalous value and it should not be added in the mean but they havent added it. If i had this paper for the exam, I would answer B because 2 and 3 I am sure are correct. 1 is definitely wrong so not A or C. So I would go by the elimination method with these kind of questions.
Edit: 4th student is wrong because he/she didnt round off the number! Mean number of bubbles cannot be in decimals!
I had already done the anomalous results and calculating it but I forgot it had to be rounded, Thank you!