9709 P52 - Jun 2022 - Q1 - 3 marks
For \(n\) values of the variable \(x\), it is given that \[\sum(x-200)=446\qquad\text{and}\qquad\sum x=6846.\]
Find the value of \(n\). [3]
9709 P52 - Jun 2020 - Q1 - 3 marks
For \(n\) values of the variable \(x\), it is given that \[\sum(x-50)=144\qquad\text{and}\qquad\sum x=944.\]
Find the value of \(n\). [3]
9709 P55 - Jun 2026 - Q1 - 4 marks
A summary of 60 values of \(x\) gives \[\sum(x-c)=642,\qquad\sum(x-c)^2=32460,\] where \(c\) is a constant.
(a) Find the standard deviation of these 60 values of \(x\). [2]
(b) Given that the mean of these 60 values of \(x\) is 95.7, find \(c\). [2]
9709 P53 - Jun 2025 - Q1 - 4 marks
For a set of 40 values of \(x\), it is found that \[\sum(x-k)=836.0,\qquad\sum(x-k)^2=25410.8,\] where \(k\) is a constant.
(a) Given that the mean of these 40 values is 124.0, find the value of \(k\). [2]
(b) Find the standard deviation of these 40 values of \(x\). [2]
