A-Level maths (statistics) help please?

Hi, could anyone help me with this question?

Data relating to the lifetimes (to the nearest hour) of a random sample of 200 light bulbs were summarised in a grouped frequency table. The mid-point of each class in the table was represented by x and the corresponding frequency for the class by f. The data were then coded using:

y = (x-755.0)/2.5

and summarised as follows:

∑fy=-467, ∑fy^2=9179

Calculate the estimates of the mean and the standard deviation of the lifetimes of this sample of bulbs.

(9 marks)

Thank you :smile:

Original post by e123c

Hi, could anyone help me with this question?

Data relating to the lifetimes (to the nearest hour) of a random sample of 200 light bulbs were summarised in a grouped frequency table. The mid-point of each class in the table was represented by x and the corresponding frequency for the class by f. The data were then coded using:

y = (x-755.0)/2.5

and summarised as follows:

∑fy=-467, ∑fy^2=9179

Calculate the estimates of the mean and the standard deviation of the lifetimes of this sample of bulbs.

(9 marks)

Thank you :smile: