Grouped Frequency Distributions (Leaving Cert Mathematics): Flashcards

Grouped frequency distributions

Data organised into classes/groups for easier analysis

When to use grouped frequency distributions

20-30 data pts, wide range, continuous data, general patterns

Mid-interval value

Value representing each class; avg of lower & upper boundary

Formula for mid-interval value

$\frac{\text{Lower boundary} + \text{Upper boundary}}{2}$

Mean formula for grouped data

$\frac{\sum fx}{\sum f}$

What 'f' represents in grouped data mean formula

Frequency of each class

What 'x' represents in grouped data mean formula

Mid-interval value of each class

What $\sum fx$ represents in mean formula

Sum of (frequency × mid-interval value) for all classes

What $\sum f$ represents in mean formula

Total frequency

Modal class in grouped data

Class interval with highest frequency

Median class in grouped data

Class interval containing median position

Formula for median position

$\frac{n+1}{2}$ where $n$ is total frequency

Why can't we find exact mode from grouped data?

Don't know exact values within each class, only modal class

Alternative name for mid-interval value

Class midpoint