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All 9 Flashcards — Cumulative frequency
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Question
What is cumulative frequency?
Answer
A running total of the frequencies up to the top of each class.
Question
Where do you plot a cumulative frequency value?
Answer
At the upper boundary of its class.
Question
What shape is a cumulative frequency graph?
Answer
A smooth increasing S-shaped curve (an ogive).
Question
How do you read the median from the curve (n values)?
Answer
Read across from a cumulative frequency of n/2, down to the data axis.
Question
How do you read the lower and upper quartiles?
Answer
Read across from n/4 (Q1) and 3n/4 (Q3).
Question
How do you find the IQR from the curve?
Answer
IQR = Q3 − Q1.
Question
How do you find how many values lie between a and b?
Answer
Subtract the cumulative frequency at a from the cumulative frequency at b.
Question
What is the 90th percentile?
Answer
The value below which 90% of the data lie — read across from 0.9n.
Question
How do you find the value the top X% exceed?
Answer
Read across from (100 − X)% of n, since the curve counts values below a level.
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Topic 4.2 hub
Data presentation
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