STATISTICS
Frequently Asked Questions
Statistics is the science of collecting, organizing, presenting, analyzing, and interpreting numerical data.
Raw data is ungrouped data collected directly from observations without classification.
Frequency is the number of times a particular observation occurs.
Data arranged in class intervals with corresponding frequencies is called grouped data.
A class interval is the range between lower and upper class limits.
Class mark is the midpoint of a class: \(x=\frac{l+u}{2}\).
\(\bar{x}=\frac{\sum f_ix_i}{\sum f_i}\).
A shortcut method using an assumed mean \(a\): \(\bar{x}=a+\frac{\sum f_id_i}{\sum f_i}\).
A refined method using \(u_i=\frac{x_i-a}{h}\): \(\bar{x}=a+h\frac{\sum f_iu_i}{\sum f_i}\).
\(h\) is the common class width.
Mean is the arithmetic average of observations.
Median \(=l+\frac{\left(\frac{N}{2}-cf\right)}{f}\times h\).
\(l\) is the lower boundary of the median class.
It is the running total of frequencies.
Median is the middle value when data is arranged in order.