Paper 6 October/November 2011 MATHEMATICS (9709/63) A Levels
لطفا برای اطمینان از عملکرد و تجربه بهتر از مرورگرهای مدرن و به روز مانند کروم یا فایرفاکس استفاده کنید.

Esme noted the test marks, $x$, of 16 people in a class. She found that $\sum x = 824$ and that the standard deviation of $x$ was $6.5$.
a) Calculate $\sum {\left( {x - 50} \right)} $ and ${\sum {\left( {x - 50} \right)} ^2}$.
b) One person did the test later and her mark was 72. Calculate the new mean and standard deviation of the marks of all 17 people.